Select the card that you want to add a logo to:
Select "Edit":
Scroll down until you have reached the "Logo Square":
Select the logo square that says "Add Logo Picture":
You are then given options to access your logo:
After you have selected your logo select the "Checkmark":
Depending on your template is what your preview will look like. Then select "Done":
If you have web links on your card, this may be shown at your preview:
Shuffle will also ask you this message: