Well, people can add them to the tactics trainer here -
How can I submit some tactical problems to be included?
Most of our problems come from games we have analyzed (as explained above). However, we would love to see your submissions which we will include if they meet our standards! All submissions must be in .pgn file(s) within a .zip file and emailed to: tacticsub@chess.com
Just wondering, how are problems added to the Tactics Trainer?