For geofence, you can pick up the pin and move it to where you want it to be. If you set your address in Hubitat's settings (Location and Modes), it should have put the pin at your home location.
I don't use Geofence since I have other presence detectors. The principle is fairly simple. When the phone goes outside the location radius, an event is generated to let Hubitat know that (presumably you and your phone are together) you are outside of the geofence and therefore, away. You should be able then to set up the Mode Manager app to use your phone as a presence device and change the mode of the Hubitat to Away. Then you can use that Away to arm your HSM app, set your thermostat (if you have one connected) to your away temperatures, etc. Likewise, when the phone returns within the radius, it generates an event that can be used to change the mode to Home which can then disarm the HSM, set your thermostat to home temperatures, turn on lights, etc.
Hopefully, this will help you get started. Anything beyond this, you will have to figure out or someone else will need to chime in with more (and better) advice.