Install the downloaded package or packages the regular way.

In the Joomla, administration navigate to Extensions → Manage → Install.

Now, when you're in Extensions: Install

1. Click Upload Package File tab
2. Click Choose file in Extensions package file and browse to the location where you have downloaded the package, select it
3. Click Upload & Install

After installing all packages, the extensions are visible in either components, modules or plugins depending what was installed.