I am sorry as this is probably the basics of the basics for you guys.
I've got 7 and I'm going through the tutorial, made some "hills" and trying to colour them using a linear gradient (width 1) from green to brown; I've clicked and done everything the same as the tutorial, however it comes out as green only - no gradient.
Are you selecting the shape before you change the effect? Under the fill section it named "select shape" Once you change it to gradient you will see a red line with nodes you can drag in and out to adjust the gradient.