This achievement can be found on the official YouTube Crystal Clash page
https://www.youtube.com/c/CrystalClashGame/about once on the page click on the About section if you cannot see the code. You can also click the in-game YouTube button at the main menu to bring you to the page.
To unlock this achievement head over to the shop in-game. Click on redeem bonus code and then copy and paste or type out in all caps in the box. Once done hit enter for an achievement.
XXYX-R0F7-Y0UT-UB3X-YXXX