First steps: WSM and pushing apps/app policy

First, thanks for taking a second to read this. This small company I'm working for is trying to roll out a group (approx 50) of thin clients (optiplex 3000s). I assisted with a rollout about 10 years ago, but during that time I was mostly focused on simply taking already-made packages and pushing them to devices, monitoring them, and making sure things looked healthy. Now, obviously, WDM is WSM and a lot of things have changed, including trying to figure out how to actually make and setup the items I want on the thin clients using WSM.

I've clearly already done something wrong. Attempting to push a basic .bat file for turning off the write filter (something I remember having to do) is throwing checksum errors, and then figuring 'app' = application, I've attempted to run an install of a small, basic app (notepad++), which has apparently caused the test thin client to be stuck on a 'reconfiguration' screen in perpetuity. 

I'm clearly lacking in basic understanding of these processes. I've spent two days trying to read the administrator guide, but can't find a basic breakdown of... building blocks, I guess. Where should I be starting with all of this?