From the Setup Ribbon Page,

In the "Projects" group, Click "Manage Users" button

The Manage Projects form will be displayed:

The manage projects form is a tabbed form with two tabs, one for projects and one for clients. We will enter our client data in first.

Click on the “Clients” tab to select the client workbook

Since this is a new database, the workbook will be empty and only the Add button will be available.

Click on the Add button to open the Clients Editor and enter the required data for your first client:

Complete the form by entering your client’s data. When you have entered all the fields you wish to enter, click on save to save the data and close the editor form. Your workbook should now contain the row you have just added. If you have more clients to enter, you can click the Add button and repeat for each client. If you need to amend any information, select the row to edit and either click the Edit button or double click the row.

When you are done,

Click the Projects tab and got to step 4