Many organizations will allow you to group (also known as baggage) with one or more other players so that when teams are created you are drafted as a group. Since these groupings affect both you and the players you are grouped with, they must accept the request.
Adding a group during registration:
If baggage is allowed you will see it during the first step of individual registration.
Use the name search box to search for the player you are looking for. Searching by email address is the quickest way to accurately find someone.
If the player you want to group with doesn't have an account you can create one for them using the Add Player link that shows up in the dropdown when you search for them. If they have an account, it will appear under the search field. Select their profile.
Once you've added a player they'll show up on this page with the status of your group.
In this case, Robb hasn't completed his registration yet so it says "Missing registration". When you add a player to your group they'll receive an email asking them to join you. Once he receives the message that a registration has been started for him, he can then complete that process.
If they did not already have a registration adding them to your group will start a registration for them. When they sign in they'll see their registration in the Events drop-down.
Upon starting their registration they'll see your baggage request with the option to accept it.
If they join your group and complete registration you'll now be grouped and the captains will draft you together.