- Download the plugin
- Unzip it and you will get a directory bp-group-suggest
- Upload bp-group-suggest to wp-content/plugins
- Login to dashboard and activate the plugin from Plugins->Installed or Dashboard->NetworkAdmin->Plugins->Installed(If you are on multisite)
- Go to appearance->Widget and add the widget "Group suggestion"
Alternatively, you can use WordPress plugin installer to upload the plugin and instal it.