1. Install and set up Github Desktop: https://desktop.github.com/
2. Clone the repository to your .minecraft\resourcepacks folder: Code > Open with Github Desktop > Clone
IMPORTANT: the repository path should be .minecraft\resourcepacks\mapwreck-6-resources (make sure there isn't an additional folder)
3. Once you've successfully cloned the repository, you can normally apply the resourcepack from Minecraft.
To update it as people add things, click on fetch origin and press f3 + T in-game.
4. Add your item textures to the folder inside of an assets that matches your area. If there isn't one, add and name one appprpriately. Once you've finished, commit your changes and push to origin.
As of 1.19.4, mojang made it a real hell to collab on custom textures live because of atlases. Due to this if you want a custom item texture added, place it in the resourcepack and message @RockNRed#0001 with the item type and custom model data number. Unless specified you need it during the event, these will be added on compile. If you want to make a change to something vanilla, please ask an organizer before doing so.
A browser tab will open for it. Once created, an organiser will review it and add it into the main branch of the pack.