This addon works via hotkeys available to you within the 3D viewport. 

While in pose mode you will be able to press Y, Ctrl-Y and Ctrl-Shift-Y to: add a key to all bones, add a key to all selected bones and reset rig to rest pose respectively.

While in pose mode, a small EveryKey button will appear on the left of the viewport.
This button contains a drop down displaying all of the hotkeys should you ever need to be reminded, and a support button that allows you to see my other work, should you be so inclined.