Once your transaction has been completed, the items will show on your account on your collection under "Items to sell". To be able to use your collectibles in the game you have to move them to "in-game". You can read more about your collection at the following link: My collection.
Once your items are "in-game", you can equip them by pressing I and going to the "cosmetics" section.
Please do notice that to use Space/utilities/decorations, you need to be on your Personal Metaverse (check ), and after that use the key binding B, to use decorations. you can read more about using space here: What is space and how to use it?
Cosmetics view; you can look at your character with all the slots view; or all the cosmetics you have in game by clicking "All Cosmetics". To equip them just drag them to the proper slot or double click on them
