G'day Shane,
When you're in the Hema app on a map view, touch the map to leave a way point, press the right arrow down the bottom to go to the Nav screen, then the Tracks button, (next to the ? button). Touch 'marks' at the top and find your way point, P1 or similar.
Once you touch this you can change the name and the coordinates to what you want.
Hopefully this helps you out.
Tim