If you already have a WordPress site but haven't been using a membership solution prior to MemberMouse, then your current members may already exist as WordPress users in the database.
If this is the case, you can easily migrate these users into MemberMouse by using the Import Wizard. Just create an import file that contains the email addresses of the users to migrate and run the import wizard.
Importing is done on a per membership level basis. Users will not be able to access the member pages until imported to MemberMouse. Read this article to learn how to Import Members with the Import Wizard.
The import wizard acts as an updater. Any information already in WordPress will be used for the new member, so to import an existing user, all that is needed is an email address. If you do enter a password into the import file for an existing user, it will be ignored.
NOTE: You may also want to consider whether you want to Hide the WordPress Admin Bar from New Members before the import, as it will only effect members added after the setting is enabled.