When you have a mega bracelet equipped and your pokemon holds it's mega stone, you can mega evolve it through the interaction wheel. (Note: You need the Cobblemon Academy resource pack in order to see the visual change in your pokemon!)
With a tera orb equipped, you can use terastallization in battle by using the gimmick button below your moves. After that your pokemon will be the new type and glow with the tera type color.
Equip the mega bracelet or tera orb to your trinket slots in order to use these gimmicks in battle. Equip the poke bag to your trinket slots in order to open your backpack with the B keybind
If you hover over a pokemon's portrait in battle, it will now show a summary of all currently revealed information about the pokemon in battle
As part of the battle UI, if you hover the tooltip button you can get a brief description of each of your moves