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I'm not sure if there is any general documentation about module installation.
However, in your XOOPS root folder, there should be a folder called "modules". Place the entire downloaded module folder and its contents into the modules folder.
Then you will want to log in, go into administration, and install the module by selecting System Admin, and then Modules. The uninstalled module should be displayed towards the bottom of the screen. Select install and then you should be able to use/access the module.