WordPress Only Login

I’m sure this has been answered somewhere but I have not had success searching.

I would like to make sure that users can only login/register through WordPress. Is this as simple as disabling registration on phpBB? I know a lot about WordPress but not much about phpBB. I just want to make sure if I disable registration the plugin can still insert new users and it doesn’t mess up any backend processes.

If there is anything else that needs to be done for WordPress Login/Registration please let me know.

Thanks!

https://www.ads-software.com/plugins/wp-united/