User management actor process subprocess

Where could i find documentation on using my own user management module instead of Bonita's inbuilt one to define my own user and their roles?

Hello,

I have the following issue.
I want that two users can start the same process, but one of the users cannot do/see the tasks of the other user.
How shall I do it?

I started with:
create User A,
create User B,
create user X.

User X is member of Group A and Group B
Process is started as Actor mapped to X, so that both, A and B, can start the Process.
Now the prbloem is, that User A can see the Processes started by B and vice versa.

Any suggestions?