I find it best to bring the Addon directories in to your Odoo addons folder via Git Hub.  The Odoo Magento Connector requires a fairly systematic import.

You are being redirected to authorize that you are paying for the one click Apps install service.

You either need a valid Enterprise Contract, to take advantage of this service, or you need to install manually:

• copy the repository modules to your server

• make them available in the addons path

• update the modules list

• install from Local Modules, not Apps.

Make sure you are a member of the Technical Features group to get access to the Update Modules List menu