I am not doing good with F key for faces can I get help

I am not doing good with F key for faces can I get help. I am on page 47 in BLender for Beginners(nook PC app) and cannot make a face between vertices.

Make sure you are selecting no more than 4 vertices.

If you have 4 verts selected and they are in a strange configuration then you might need to smooth them out before a face can be generated.

With the verts selected, Ctrl+W -> Smooth, repeat as required.