On the Admin dashboard click on Account and then Users.
Under Show Users, click on Remote Users tab.
Click on the Action button and select Settings.
Go to the Credentials tab and look for Remote Campaigns. This is where you select the campaign to assign the Remote User. (Note: RVM (Ringless Voicemail Campaign) and SMS Campaign should not be in the option since those type of campaigns have built in Remote Users).
Once done, click on Apply Changes.