Um...my first response is RTFM 
Now that I have the smart ass answer out of the way...
Look under the Selection menu on the right side of your screen. There you should find all the tools and shortcuts needed to select faces, point, clusters, edges and so on. There you will also find selection methods such as Raycast, Lasso and paint selection modes to name a few.
The easier answer would be hit the U key to active the raycast face select mode or hit Y to enter box select face mode. Once you have that face selected, hold down ALT and right click, select the extrude face option...there you go.
Honestly though, go through the tutorials and manuals. Believe it or not, they are not bad and can help a lot.
Vmpre