Utilities > Options > Users ... Double-Click on a user name in the list to change their access level.
Utilities > Options > Contact Types  - this allows you to make changes to contact type information

User - (standard user)
   - Has access to all contacts in contact types that are Public
   - Has access to any contacts where they are the record owner in contact types that are Semi-Private
   - Has access to any contacts where they are the record owner in contact types that are Private
   - Has access to any contacts of a Restricted contact type where they are listed as having rights

Power User
   - Has access to all contacts in contact types that are Public
   - Has access to all contacts in contact types that are Semi-Private
   - Has access to any contacts where they are the record owner in contact types that are Private
   - Has access to any contacts of a Restricted contact type where they are listed as having rights

Registered User (Primary Owner of Software) = ADMINISTRATOR
   - Has access to all contacts in contact types that are Public
   - Has access to all contacts in contact types that are Semi-Private
   - Has access to any contacts where they are the record owner in contact types that are Private
   - Has the right to add users
   - Has the right to change access levels to system Contact Types
   - Has the right to assign contact types that are Restricted (you can assign who has access)