When adding a new user, they won't have any Profiles set up for them to be able to send posts, view streams, or generate reports. So if you would like this new user to be able to perform any of these actions they would need to either add new profiles, or have an already existing user share profiles with them.
If you would like them to be able to access any of the profiles you or any of your team members have already set up, then share the profiles instead of having them add themselves.
This is for a couple of good reasons:
1. If you share a profile with a new user, then they will have access to all the reporting data already gathered by your account, and so they'll be able to generate reports reaching back to the point you had added this profile, otherwise they'll only be able to generate reports displaying data from when they added it themselves.
2. If there is more than one user managing specific accounts, by sharing profiles, all users will be able to see which messages have been scheduled and when.
3. Each account has a limit to the number of profiles they can add, so if each user adds their own profiles this limit will be reached very quickly. If, however, the users in this account share profiles they can all have access to a great deal more profiles.
If there's an account on a Small plan, which allows up to 3 users and 48 profiles, if each user adds their own profiles, then they can add 16 profiles each.
If instead one user adds 48 profiles and shares them with the other 2 users, then they'll all have access to these 48 profiles.