Greetings

I decided to write because I've been banging my head for a lot of time. I need to set my RB951-Ui to connect to ExpressVPN, fulltime. I have been checking online a lot, but I could not find complete instruction how to do it. Everything I found is partial commands, nothing for webui or winbox.
The firmware is 6.47.1.
Is it possible for someone to make a detailed user-friendly instruction that everyone can use?
The same will be good for all VPN providers.