Trove

You can first equip a Gem at character Level 10. You will need a Water gem for this slot (every few levels another slot will open up for water, fire, or air gems to be equipped). Once you are Level 10 and have obtained a gem (found in Elemental worlds, gem boxes, and the Shadowy Market), open your character sheet and hit the bumper to switch to the gem page. Pick an open slot and then a gem from your inventory to slot it and unlock the achievement. Gems are a great way to increase your Power Rank, so make sure you always equip better ones when you get them and fill every slot once it unlocks.