Beginner learning Mirth Connect basics — need help with file naming and workflow setup

Hi everyone, I’m new to Mirth Connect and trying to start from the most basic setup — reading an HL7 file and writing it out as JSON.
I’ve got my channel running, but I’m still confused about how to make variables work for file naming and output.
I’ve uploaded my example project to GitHub so you can see what I’ve done so far:
:backhand_index_pointing_right: GitHub - jruizzd/mirth_orm_to_mwl · GitHub

Any feedback or beginner‑friendly explanations would be really appreciated. I’m just trying to understand the fundamentals before moving on to more advanced workflows.