The submission process has two phases. You first need to make sure your opponent does not have much stamina available. The lower you can take it, the better chance you have for a successful submission. One of the quickest ways to deplete your opponent's stamina is by using Rest Hold. To perform Rest Hold, you can either grab your opponent from behind or grab him or her once and then press [Grab] again. Once you have successfully executed that, try to weaken one of his or her limbs and work towards the submission. Going with multiple submissions can drastically damage the limb and make the submission easier. Also, keep the submission stats of your wrestlers in mind. There are wrestlers that have submissions as their finishing moves as well, which makes forcing a submission much easier.