1. Click Projects in the left navigation panel..
2. Select a project from the list.
3. Select Users from the top navigation panel.
4. Click Add User in the upper-right corner.
5. Enter the first few characters of the user's name or select from the pick list. (If the project's billing method is based on the project hours, then you won't see the Rate Per Hour field here.)
6. Select multiple users to add them in bulk.
7. Click Add.