I'm just going to do basics here, my toughest part was learning nomenclature, and sequence, so if you're like me, hopefully this'll help:Firmware:
Is 'burnt to your MS unit, similar to a laptop's 'Bios'Software:
is what runs on your laptop (usually Megatune or newer Tuner's studio) and allows you to 'tune' and view megasquirtini:
Comes with, and is specific to each 'firmware' version, is loaded into 'software' (megatune's 'configurator' enabling it to
communicate with each particular firmware version.MSQ:
The tuning file in Megasquirt. You can save copies in your laptop to look at off line, or transfer to a buddy's MS (with appropriate ini)
First you'll need firmware:http://www.msextra.com/doc/ms1extra/Downloads/
For 420a build, you'll need 'extra' version. There's 'hi-res' extra available, it allows more refined tuning if you have huge injectors.
Firmware needs to be 'burnt' to MS.
Then you'll need to install megatune, and appropriate firmware version ini.
Next you'll need to do 'settings', a thread in itself