Hi Chris!
In the basic template you just fill out everything up to PnL from left to right. In the column "Direction" you put "S". Can be s or S, both work. For long it's L or l.
You can delete all columns except the ones with the red header:
The important fields to fill are "Direction" (S for short), Entry (entry price) either Target price or Exit price and the position Size.
Make a new copy if you want to, I've made an edit in the template (to grey out the Direction fields when there's no input)