The "Guardians of Ember" key is a conventional Steam key - use it to add the base game to your Steam library in the usual way, as described here.
The "Guardians of Ember - Wings In-Game Content" and "Guardians of Ember - Immortal Edition" keys are NOT activated in Steam, they are instead entered within the game as follows:
- Open the Steam client and start Guardians of Ember.
- Log into the game.
- Open the Frozen Ember Shop via the blue crystal icon located on top row of the screen.
- Navigate to "voucher" on the left side of the shop window.
- Insert the voucher in the top field and insert "0" in the bottom field and hit enter to unlock your items/version.
- You will find your items in your inventory.