Make sure you already downloaded a zip file of the plugin to your desktop.
1. Login to your WordPress admin dashboard.
2. Under the dashboard menu, hover your mouse over "Plugins" and click on "Add New".

3. Click on €śUpload Plugin€ť and then on €śBrowse€ť. Chose your plugin€™s zip file and then click on €śInstall Now€ť.

4. Click on €śActivate Plugin€ť.

Note: The newly activated plugin will show in the sidebar menu. If a setup of the plugin is required, it will show an option to complete it.