Question GIMP help needed~

heres this tut I'm doing and it says I need to alpha select....
What and how do I do that?

 

Go to the layers pallet and right click the layer you wanna select.
Look for it in the menu~

 

I still can't find it -.-

Oh, and if it doesn't trouble you, how do you displace something? I really hate these tuts... they confuse me...

 

Filters>map>displace
And go to the layers pallet (control + L )and right click the layer you wanna alpha to selection.