You can easily change your club emblem by visiting the Matchday website. Just follow these steps:

1. Go to matchday.com and log in using the same credentials you use for the Matchday Champions app.
2. Click the pencil icon in the upper-right corner of the screen.
3. Click on “Change crest” and choose the emblem you want for your team.

Note: If you use Apple ID login, you'll need to retrieve your email address from the in-game settings.
From the main game screen, tap on your club emblem in the upper-left corner, then tap the Settings button (the cogwheel icon in the upper-right corner).