Simply go to the 'Plugins' page, search homebridge-wemo and click 'Install'.

This will only work if you are using a platform which installs plugins globally.

sudo npm i homebridge-wemo -g

If you use the Homebridge UI or HOOBS then a configuration screen will appear after installing the plugin where you can configure the plugin. You must click 'Save'.

See the Configuration page for JSON configuration templates and other optional settings if editing the configuration manually.

And voila your Wemo devices should be discovered on your local network and added to your Homebridge/HOOBS instance.