cant edit npc sheets as dm

trying to work on a monster and the character sheet wont let me add actions to the npc 

If you could describe what you are trying and what is happening, it might help. The expected procedure is click the plus icon to create the new action and enter the name of the action first. If you enter any other field first, I have noticed that the action can disappear.

i try to add the plus icon in the action tab but all it gives me is a . then clicking the wheel option makes it go away 

As you may know, due to the amount of character sheets, Roll20 actually are not the ones who create them- instead most sheets are created by various members of the community. This GitHub repository contains all of the Sheets currently available. Since this is not a Roll20 Official Sheet the best thing for you to do to get help would be to head to the Character Sheet forum to ask in our help forum specifically dedicated to the topic. 

@TwilightWoods: Is there a reason you don't think this is an official sheet?