Navigate to the Assets tab in the left hand navigation bar

Select Competitions

Click on the competition for which you want to change the logo. In the below image American Football Festival is the competition

Hover over the competition logo and select Replace

Navigate to where the new logo is located

When happy, select Open or double click on the desired logo

Once selected you will enter the Edit Image section. Position and scale the logo as required

Once happy, hit Save

Hit Save at the next screen and you have successfully changed the competition logo