NOTE ExpressionEngine 2.5.3 + is required to run CartThrob 2.2+
Please note, if you are doing a fresh install or upgrading from a previous version, it is always recommended that you backup your site's database and files. Always back up your ExpressionEngine database before installing or upgrading new extensions!
Upload / Overwrite existing CartThrob files
Download the newest version of CartThrob. The newest download is always available here in your downloads.
Using an FTP program, backup any modified files, or files located in
Cartthrob > third_party folder.
Upload the CartThrob files to the appropriate folders on your website. All CartThrob folders and files found in the "system" folder are intended to be placed in your ExpressionEngine folder, regardless of its current name ("system", "admin", "expression_engine", etc.) All files should be uploaded in ASCII/text format, except images which should be uploaded in binary format.
Places all of the directories found in system/expressionengine/third_party into your /system/expressionengine/third_party directory. Place the themes/third_party/cartthrob directory into your /themes/third_party directory.
If your FTP application supports it, we suggest uploading files and folders using using the "merge" method. Transmit on the Mac supports folder merging. Check preferences > transfers > uploading folders > "Merge the existing folder"
Go to ExpressionEngine's settings > Addons > modules. On the top right click "run module updates".