The process of implementing video ads in Google Ad Manager is a 5-step process: 

1. Step 1: Create Ad Units

   Ad units are the spaces on a publisher’s inventory where they want to display ads. The first step to running these ads is creating ad units to run ads on. Here’s how you can do it:
   
   Sign in to your Google Ad Manager account.
   
   Click on Inventory >> Ad Units.
   
   You need to select a hierarchy level for the ad unit. This can be done by either selecting a parent ad unit or the ad unit will run at the top.
   Click on New ad unit. 
   
   Now enter a Code. This will help in identifying the ad unit in the associated ad tag. For example, mysite_economy_home. 
   
   Provide a Name and Description for the ad unit. 
   
   Select a size for the ad unit. You can select two sizes: Fixed and Smart. 
   In case you are using Video Solutions offered by GAM, the next step is to enter the default master video and companion slot sizes. Master video size is the size of the video player in its most favoured aspect ratio.
   
   Select Target window which has two options: Top and Blank. Target window is important as it defines the window in which the landing page will open.
   
   Set Frequency Caps which defines the number of times a user will see the ad on their screen.
   
   Click on Save.
   

2. Step 2: Video Ad Tag Generation

   Once you have created the ad unit, the next step is to generate ad tags. Ad tags are important because they contain all kinds of information required in a video ad request. This can include anything related to the companion ads or the master video ad.
   
   Here’s how you can generate ad tags for the video ad units: 
   
   Click on Inventory >> Ad Units
   Select an existing ad unit and click on Tags.
   Select the Tag Type. Most common is the Google Publisher Tag.
   Select the SDK type. If you do not have an SDK, opt for no SDK. In most cases, a publisher is using the Google IMA SDK, so select that. 
   You can then add optional parameters in the tag. 
   Copy the generated ad tag. 

3. Step 3: Creating Video Line Items

   Once you’re done with generating a video ad tag, the next step is to create a line item. But before that, defining orders is mandatory. Once that’s done, here’s how you can proceed with line item creation;
   
   In your insertion order, click on the New Line Item button. 
   Click on Video. 
   Assign a name to your line item. 
   
   The next step is line item targeting. For these ads, there are four kinds of targeting available: Content targeting, Position targeting, Request format targeting, and Request platform targeting.   
   
   We’ll cover the three major kinds of targeting: Content, Position, and Request Platform Targeting. 
   
   Content Targeting: Through this, publishers can monetize video content more efficiently by targeting ads to that specific content. This is done by collecting metadata by connecting your Content Management System to Google Ad Manager. Here’s how you can do this;
   
   Click on Video >> Content Sources >> New Source. 
   Enter a source name, after which you will need to select a Content Type. 
   Choose one of the three available type options: MRSS Feed, Ooyala, Brightcove. Each type requires individual credentials. For example, for Ooyala, you will need to enter API key and API secret. 
   Next step is to select a sync rule which is of two types: Automatic and Manual. 
   Click on Save. 
   
   Position Targeting: Through this, publishers can target video line items to specific video positions such as pre-roll, mid-roll, etc. But for this, the first step is to set ad rules. This helps in setting parameters such as how long the ad will be played and others. Here’s how you can do it:
   Sign in to your Google Ad Manager account.
   Click on Video >> Ad Rules >> New Ad Rule. 
   
   Pick and enter a name for the rule, followed by selecting the status, and either of the two ad rule types: Standard and Session. Configuration of either of the rules is a lengthy process and requires a thorough understanding of settings. 
   Next step is to choose schedule time for the rules. Select Unlimited if you want the ad rule to run indefinitely. 
   
   Click on Targeting to match the ad rule with specific ad requests. 
   
   Click on Save. 
   
   Request Platform Targeting: Publishers can use this to target video line items to specific ad request platforms. Here’s how you can do this: 
   Sign in to your Google Ad Manager account.
   Select a video line item or create a new one. And then click on Settings. 
   Under the Add Targeting section, click on Inventory Type. Select any of the available inventory types including In-stream video, App display and out-stream, Web display and out-stream. 
   
   Click on Save. 

4. Step 4: Adding Creatives to Line Items

   Video line items require addition of creative sets into them. Here’s how you can do it: 
   Click on Delivery >> Line items. 
   Select and open your video line item. 
   Click on Creative >> Add Creative >> New Creative. 
   You will then need to select a VAST creative. Ad Manager supports four kinds of VAST creatives: video, overlay, redirect, and set-top box. 
   Configure settings according to your preferences and click on Save. 

5. Step 5: Creating Reports 

   Reporting for video ads in Google Ad Manager works exactly the same for any other ad format. Here’s an extensive guide on how to generate reports in GAM.