SmartProxy can be installed - here.
Open the SmartProxy extension Settings -> click on "Proxy Servers" and then "Add Server". Give a name to your server, then fill in the rest of the proxy details and click "Save".
Now your proxy server should be set as default server, so now click on SmartProxy extension icon and choose "Always Enable".
Open our IP checker and see if your IP changed.
That's it, you're all set!