If you have acquired a Costume/Guardian of Epic grade or higher, it will be in a pending confirmation state for 7 days from the acquisition date, and it will be automatically obtained after this period.
During the pending confirmation state, you have the opportunity to change to another costume of the same grade 5 times, with 3 changes allowed for Legendary Grade Costumes. Please note that there is a cost for each change.
If you wish to obtain the Costume/Guardian immediately, you can do so by opening the following menu:
Costume > Pending Confirmation
Guardian > Pending Confirmation