Video Walkthrough:

Instructions:

1. From the custom game lobby screen, press Settings in the top right.
2. Press the Share button in the top right of the Settings screen.
3. Press the dropdown and select Upload to Existing Code.
4. Fill in the import code you would like to upload to (in this case, Q74P7), and press Continue.
5. Wait for the code to be updated, and then copy the code if needed.