The PCT calling system uses TEAMS to assign phoners to campaigns.  Each campaign has one team assigned to it.  This is found on the "Agent Options" tab when you are editing Campaign settings.
You can manage which users are assigned to which teams in the Administration | Teams section of the calling system's admin area.
To adjust the team(s) that a specific user is assigned to, go to Administration | Users.  Click on the user's row, then on the Edit button.  You can then add or remove team assignments for the user, and click Save.
To adjust the users that are assigned to a team, go to Administration | Teams.  Click on the team's row, then on the Edit button.  You can then add or remove users, and click Save.
Be sure that each team has at least one clicker user, and for best performance, don't have the same clicker supporting more than one team at the same time.
NOTE - be careful about assigning the same user to more than one team that will be active at the same time.  This can be confusing to the user, who will get a mixture of calls from more than one campaign, and can make it difficult for the calling system to maintain appropriate pacing for the campaigns.