Polaris does most of the work implementing SEP-24. However, Polaris simply doesn't have the information it needs to interface with an anchor's partner financial entities. This is where .DepositIntegration and .WithdrawalIntegration come in.
Polaris expects developers to override these base class methods and register them using .register_integrations. The code will be executed from inside Polaris Django Commands, which should be run in a separate process from the web server running Polaris. See the stellar-anchor-server project, specifically the docker-compose.yml, for an example on how to run the Polaris web server and management commands.
polaris.integrations.transactions
polaris.integrations.register_integrations