Select the Codenames option, then enter the codes at the Secrets Screen. Save your Codename after entering the code.

Select any level - Enter PASSPORT on the passcode screen.
Alpine Escape - Enter POWDER on the passcode screen.
Chain Reaction - Enter MELTDOWN on the passcode screen.
Countdown - Enter BLASTOFF on the passcode screen.
Deep Descent - Enter AQUA on the passcode screen.
Double Cross - Enter BONSAI on the passcode screen.
Enemies Vanquished - Enter TRACTION on the passcode screen.
Equinox - Enter VACUUM on the passcode screen.
Island Infiltration - Enter PARADISE on the passcode screen.
Night Shift - Enter HIGHRISE on the passcode screen.
Phoenix Fire - Enter FLAME on the passcode screen.