What ever you do, don't apply the glue as randomly and as messily as he does in that video!
He gets it everywhere, way past the hairline.

To know exactly where to apply the glue, some people mark the hairline with a make-up pencil.
I prefer to go around the hairline edge pressing the teeth of a comb into my scalp that then leaves indents, but eventually you'll work out your own method that suits you.

Good luck!