Easy! Just log into your Dashboard. You can access this by going to Squadlocker.com and logging in with your credentials at the top right of the page. Once you're in, just find the store you'd like to make the logo change to and click "Edit." From the left navigation bar click on logo and then click on "Upload your logo". Select the logo file you would like to use, by either double clicking on it or by highlighting it and clicking on open.
Don't forget to click Save!