Where do users login?
You may customize the login address. On default installs, you point your members to [your domain]/login/ . For example, https://wedowordpress.com/login/
Where do members manage his account / subscription / payments?
You may customize the account address. With default settings, you point your members to [your domain]/account/ . For example, https://wedowordpress.com/account/ . If a member is not logged in, they will see a link to the login page.