You may wish to back up your existing theme - see How do I back up my Big Cartel theme? - before applying these instructions.
Changing your theme to a standard Big Cartel theme (Uninstalling a theme)
To install a standard Big Cartel theme (i.e. uninstall an Aarcade or other theme), navigate to the Customize design > Themes and click the Big Cartel theme you wish to install. Note if your preferred theme is already selected, simply click it again if you wish to select this theme.
Wait a moment for your preview to update according to your selection and then Save and Exit the Customize design area.
Restoring a backed up theme
To restore a backed up theme - see How do I back up my Big Cartel theme? - you will need to unzip your backup file, open up each file in your preferred HTML editor, and copy each to the correct theme file in the Customize design > Advanced panel of your Big Cartel admin area.
Using a non-HTML text editor — like TextEdit, Word, etc. — may corrupt your HTML files as soon as they open.
Use a HTML editor like Coda or Google how to correctly use your text editor with HTML before opening your backed up theme files.