The steps I've taken are below...
Log into Web Admin>Devices Interfaces>Add Device>
I added the manufacturer "Honeywell" and selected it
Device Category "Interfaces"
Add device template
I then chose "It's a simple, generic serial device controlled by RS232, Ethernet or USB, which you'll control with Pluto's GSD and embedded Ruby snippets (very easy). Examples: Lighting control, alarm panels, surveillance cameras, thermostats, weather stations, a/v equipment with RS232 ports, etc." and listed the model number as "Vista-15P" and clicked Add.
I did not choose a room for the device and chose "CORE" from the controlled by dropdown.
Now I click on Advanced and input the IP Address of my device "192.168.80.114" under device info
My next step was to click View in the Device template field
I added the Controlled Via Device as "Computers" like the apex template
Now I check the Is IP Based box and select Ethernet as my Comm Method
Under Device data I added "TCP Port" added that comment "Port to connect to" set a default value of 80 and check both Required and Allowed to Modify. I also added "TCP Address", set the comment "IP Address" left the default value blank and check both Required and Allowed to Modify.
Then under Commands I added "Security Panel" and "Ruby Internal Commands"
Under Events I added "Reporting Child Devices" and "Sensor Tripped"
This is as far as I've gotten and I have no idea what to do next. I obtained the source code for a Homeseer plugin that was written to interface with this device if that helps, however I was unable to really understand what it's doing. That source code is attached.