Firstly, make sure you have created a team account. Instructions on how to create a team account can be found here.

1. Go to "Account Settings" (click the three dots in top right corner).

2. Click the "Team" option.

3. On the "Team" screen you can invite users to your account (credits show on the right side of screenshot). You can also purchase additional accounts for more users (shown on the left side of screenshot).