Launch Rune Gui in Roblox.; Once you are at the main menu, press the codes (ABX) button in the lower right corner. The text box will appear. Copy and paste the code you want to use.

Open Blue Lock Rivals on Roblox. In the game’s main lobby, look for the Codes button at the bottom of the screen. Click the button, then enter a working code into the "Enter Code.." ...