Partner avatars are part of registered users' collections.
Registered users can create and manage their avatars through their account and import them into applications. If they want to try out a new app that supports Ready Player Me avatars, all they have to do is sign in with their account.
Users access their avatar collection on the Ready Player Me website. Their collection is not reachable from your partner subdomain.
However, they are able to sign in and retrieve their existing avatars or create a new one within any partner app.
Creating a Ready Player Me account is entirely optional for the user.