Open the match you want to edit from the 'Matches' page
Scroll down until you find the Logo section
Click on the upload icon to open the Media Gallery popup
Choose the logo you want to set to the team
Confirm with the blue button
Done! You set the logo for the team.
If you want to unset that, simply click on the trash icon next to the logo preview. The image will remain inside the Media Gallery but will be unlinked from the team.