Create Magic Item with Activations
 

I've searched the forums and I haven't been able to find HOW to add Activated Abilities List item to an magic item.

I'm specifically trying to edit the Mask of the Red Mantis, as the version I have has only 2 of the activatable abilities made (darkvision and perception +5), but I'd like to add see invisibility and deathwatch checkboxes.

Any help is appreciated.