The link in the error message lands on Welcome to the Azure Video Indexer Developer Portal which has a link to View ARM APIs. These APIs will allow you to manage resources i.e., list, create, update. I believe Generate - Access Token is the equivalent of the classic GetAcccountAccessToken
you've been using for classic indexers.
Having said that, ARM is essentially managing your Azure resources so it's more your infrastructure code. In other words, having a pipeline that will create or remove Video Indexer accounts. Once you use ARM to create the resource, get the access token for the ARM resource, and use https://api-portal.videoindexer.ai/api-details to interact with your video indexers.