It's pretty easy actually but you do have to be at work to set it up.
Go to
Sign In from a computer that's behind the firewall (I think the operations computers don't work but the one in the conference room should) and sign in with your ActiveDirectory username/password. You should get to a page that offers you to set up two-factor auth via an app on your phone, they suggest the Microsoft one but I use the Google one just because I have other keys stored there already. Once you have that set up (use the 2FA app to take a picture of the QR code) you can go to the webmail site from home, sign in, and then enter the temporary code from the app.