Step 1: Components
You will need a PICKit 3 debugger which you can get for around 30$ here and also an 8-pin SOIC clip. You can make one which will work, but takes some time, by following these instructions, or you can order this one which I recommend. Jumper wires you can get here.
Step 2: Connect to MicroLight
Remove the batteries
Step 3: Connect to Debugger
Connect jumper wires from SOIC clip to debugger. Be careful to not mix up the connections.
Step 6: Open MPLABX and Connect PICkit 3
Step 7: New Project
Step 8: Standalone Project
Step 9: Select Microcontroller
Step 10: Select Header: None
Step 11: Select Debugger
Step 12: Select Compiler XC8
Step 13: Project Name & Folder
Step 14: Import Source Files Into Project
Download source files from r/glovinghacks and paste them in the project folder in Finder. Then in MPLABX right click on Source Files and Add Existing Item (configuration_bits.c, Initialization_MicroLight.c, main.c). Right click on Header Files and Add Existing Item (Initialization_MicroLight.h).
At this point you can edit and modify the source files as you wish. It is recommended that you only change things in the main.c file, specifically only in the while(1) loop, more advanced programmers can modify the interrupt routine if they wish. Global variables can be created in the Initialization_MicroLight.h.
Step 15: Go to Customize Menu
Step 16: PICKit 3 Program & Power Options
Select these settings and click Apply.
Step 17: Program MicroLight
Note: If you are trying to read hex file in this step, please consult r/glovinghacks, as some glove sets have their firmware code protected so you will not be able to read and revert to the original firmware. (Once you reprogram the microLight once, the original firmware is lost.)
Step 18: Downloading New Firmware Onto PICkit 3
Note: If there is an error that has to do with voltage, go back to Step 16 and reduce voltage to 4.5V
Step 19: OK
Step 20: Programming MicroLight / Programming Complete
Step 21: Reprogramming Original Hex
To reprogram the hex file you extracted in Step 17, create a new project but this time select Prebuilt (Hex, Loadable Image) Project. Then browse for hex file and create project. Follow from Step 17 on.