How do I add custom fields to my logins? Or do I need to use the windows version to do this?
I can't see any way to do it in the Android app either.
1Password on Android does not have the ability to add custom fields yet. We can only read custom fields added using 1Password on a different platform. This functionality is very important to us and we plan to look into adding it in a future update. I'll add your vote @mixgenio!