@Startgroup I have on my backlog a plan to create a tutorial for a nice extension for Chrome that allows you to create POST and GET requests. Wrapping your head around exactly what those requests really are goes a little deeper, so I'll add to my list a basic overview of that.
For now, see if poking around with this extension helps. Make sure you have the Tinker application flashed to your Core. See my brief tutorial on how to send a POST request to turn on D7 from this extension here:
You probably were lost with the jflasher app because you had not programmed your 
Core with an application that you could talk to. Maybe you will have better luck trying my Simple Spark Core Controller
GitHub - technobly/Simple-Spark-Core-Controller
(run the example first! and then you can learn how to customize it)