MijoForms is easily installed as any Joomla component. That should be done through your site's backend.
Once you log in, you should open the Extensions => Install/Unistall section and click on the [Browse..] button in the Upload Package File section. Navigate to the same MijoVideos file you have downloaded earlier and select it. Then click on the [Upload File & Install] button to start the installation. It will install :
1. The main MijoForms component
2. Front-end form module and plugin
3. Language files