If an add-on is obtained from a source other than the X-Cart App Store, you can upload and install it as follows:
1. In your store’s Admin area, click My Add-ons to open the My Apps page of the X-Cart App Store:
2. On the My Apps page, locate the Upload addon button and click on it.
A pop-up titled Upload addon appears:
3. In the Upload addon pop-up, submit an add-on package by clicking the Select file button. The file should be a .tgz, .tar.gz or .tar archive.
This starts the installation process. Once complete, the addon falls into the list of installed addons.