In order to install modules on your OpenCart website you will need to navigate to the Administrative area website. Once there you will have to go to Extensions -> Installer
Now you will have to go to your System -> Users -> User Groups and grant permission (only for access and modification) to administrators or other groups.
Once you have done the above step you will have to go to Extension -> Modifications and refresh the modifications cache. You will also have to refresh the theme cache from your Dashboard.
And now you will have to navigate to your Extensions -> Extensions and activate and setup the module.