I am pretty sure your 2007 Subaru uses standard CANbus. In fact, when I saw 2007, I checked this resource to see if your car even uses CANbus. It does, thankfully!
I have a 2010 Forester that uses standard CANbus with no problem. My 2004 Impreza uses ISO-9141, so definitely CANbus does not work for that one.
Let's get started then.
I would suggest checking out the sample apps at carloop.io:
As I mentioned earlier, I recommend trying the VIN Reader app.
Flash the app to your Carloop, then read the VIN on your browser screen.
(I had forgotten that you don't even need USBserial for this.)
After that, try getting the source from GitHub and then build and flash the app yourself.
That will get you familiar with the aspects of how to program your carloop.
After that, then it becomes all about programming your carloop to do what you want it to do.
Let us know how it goes, and also let us know step-by-step if you run into any issues and we will try and help you out.