Putting in the new pen
When it is out, place the pen you want to use, with the pencil grip wrapped around it, in the pen holder and close it. If there is a gap in the holder put that towards the back.
Adjust the height of the pen by putting a scrap piece of paper between your project and the pen and adjust the pen until it touches the scrap paper then pull it back up just a smidgen. The first few times you try this, you may have to adjust it slightly but it will work.