Before installing any module, we strongly recommend backing up your files and database (via FTP).
If you do not know how to do this,instructions are HERE.
First, determine the type of module (vqmod/ocmod).
For VQmod modules, VQmod must be installed first.VQmod system.
If the module is OCMOD, your version of OpenCart must be v2.x - in this case, simply upload module in administration.
VQMOD modules: Just copy the contents of the module into the root folder of your e-shop.
OCMOD modules: The installer runs in the Opencart administration -> "Extension installer"