Get out after midnight, find Cassiopeia, roughly follow its extended line toward the horizon to Capella, the only bright star in that region.
The next brightest star farther down to the north is Menkalinan. One more time the same distance, you'll see NEOWISE. It's faint, but quite long; several times the size of the Moon.
Here's a more accurate guide, made by Pete Lawrence.
Here you can see NEOWISE's exact position day by day, its relative brightness, and the direction of the tail.