Need in-depth knowledge about github on this crucial phase

Hello, GitHub, I recently got a project from a client, multiple developers working on the same project from different locations. the owner of the website asks me to work on GitHub. but I am totally new on GitHub, I have been watching GitHub tutorial on youtube for 1 hour but no success. the website is built in Wordpress cms with different plugins installed, and files are hosted on Namecheap. is this website support GitHub? how I can sync all files of this project on my local machine and work as a team member. The project is in the development phase, and the two developers working on issues fixing. Waiting for your kind response.

Please follow these instructions
https://medium.com/@danyalraja/easy-start-git-using-command-line-d95f8eb559d4