Hammer isn't something you can pick up and learn in a day. It will take a while, be patient.
I used
this tutorial when I started, it covers the basics of hammer and how to use the more important tools (it's technically designed for Half-Life 2 mapping but it doesn't matter).
Google is your friend. Also keep Political's link and
this link handy. They'll help a lot. There are also a lot of good tutorials on Youtube.