Sure!
Firstly, locate the 'servers' tab on the website. Click it and you should see a list of servers organized by EU, CA, AU, and US.
Select the division in which you'd like to play, then click that tab.
Find a server that says 'lobby' and open up minecraft.
Go to the multiplayer tab on minecraft, then click add server.
Put the IP in exactly how you found it from the website, and click 'Join server.'
If you do not have donator status, (donator status is a paid-for in game perk allowing you to join full servers and not be kicked) consider purchasing it.
It can be purchased here:
http://www.minecraftsurvivalgames.com/account/upgrades
If you cannot purchase donator, here are a few tips to join servers and avoid being kicked:
1- Play on the CA and AU division servers. They have slightly less donators playing, making it a bit easier to join.
2- Join higher numbered servers. Most donors join the first one they see, which is generally a lower number, so joining higher number servers can help avoid donors.
3- Play at night, or close to it. Most players play during the day, so if you play around 9-10, server traffic is significantly down, making it easier to join and stay.