GtkRadiant/Getting around in GtkRadiant

Now that you have downloaded, installed and started GtkRadiant, you will probably start to draw around a bit with your mouse, and you will see that where ever you draw on the grid, a red square will appear, now you may think, is this really the program all others made those awesome maps in, the answer is probably yes, so, how is this done, first of all, you have to learn the interface.