To join a server is as simple as typing this in console:
> connect server_ip

so to enter our servers would be:

connect 5.39.90.48:27016
connect 5.39.90.48:27017
connect 5.39.90.48:27018
connect 5.39.90.48:27036
connect 5.39.90.48:27037

If you dont have a console, click here: How to show the game console

Also you may want to add a server to favorites for future games. To do that just click "browse community servers" ingame

See Image 1 (click)[oi61.tinypic.com]

go to favorites, add favorites, copy/paste one of the ips above and click on accept, as the screen shows.

See Image 2 (click)[oi61.tinypic.com]

And voilà, enjoy the server whenever you want.