In case this isn’t obvious, most of what I just wrote should be done on the Github web page.
That is the best way to work with teams in UE4, but there is a hacky way of avoiding all the forks and pull requests. Create an organization, add all your developers to it, and then copy your current repo into that organization, then have each of your developers push commits directly to the project. If you have a small team, this might work ok. If 2 of you ever try and push a commit at the same time though your repo could get corrupted. Luckily Github allows you to roll back to a previous change though.
Personally I prefer the fork and pull method, especially for teams larger than 3-4 people, but it’s up to you really. They both work.