You have two ways to add an agent to your brokerage.
Via the People's page
First way is to click 'New' in your Brokerage People's page:
2. Make sure Type is Agent, you chose their office, Add their name, and if they are paid out as a corporation, add that into the org field, this will open the payable name field, choose organization in the dropdown and add their email, save.
Via a Deal
The second way is to add an agent on the fly in a deal, if you already have a deal created and you need to add another agent from your brokerage to that deal, then click 'New' in the people's page of a deal
2. It will open the 'Adding Deal Access' popup window, from there, you click add new agent (Important, this option is used to add your own INTERNAL agents, not outside ones)
Fill in the edit profile window as shown above in the second step.
Here's a more in-depth video on contacts.