2
Admin preferences main settings
Choose main page, user profile.
Is user logs in the profile page will ben the main page.
If you mean the login block, see block settings.
See also your question with reply:
https://xoops.org/modules/newbb/viewtopic.php?topic_id=72681&forum=20&post_id=333898#forumpost333898
I see you have a lot of questions. Without being rude, I advise you to experience and explore xoops more before asking everything. Because that way you prevend that other users won't answer your questions anymore.