Choose your MODs during the dinosaur selection stage of a Modded Battle. Once you select your dinosaurs, you can choose a MOD for them. If you want to swap out the current MOD for a different one, simply tap the MOD icon on top of your dinosaur to remove it, and then you can add another one. If you want a different dinosaur, simply tap the dino to remove it and its attached MOD will return to the roster. You can then reselect it, or choose a different one for your new dino.

During battle, your MODs are used automatically! Some MODs are applied at the beginning of the battle, and other MODs are only applied after certain criteria are met, such as at the end of the player's turn, or if your dino has 0 HP. There is nothing that you need to do in order to activate the MODs, don't worry!