You cannot require that fields be filled before a save is allowed. You can alert a user with something like a popup messge just before or after a form is saved, but that's it.
How can I set it so that if someone types in the Action Column, the Date Identified, Target Date and To Be Completed By columns have to be completed in order to be saved? Maybe make them red in color so the user sees that the fields have to be filled in before completion of the form? I'm sorry, this is my first time coding forms like this so it might take me a while to figure things out.