If you both want to work on the same project, then you shouldn't have forked the the repository twice. You or you friend (not both) should fork the repository, then both of you should clone the forked one in local (permissions need to be granted by the one who forked repository).
Once this is done, when members of the project want to know if there are new changes on the remote, they can do git remote update
or more commonly git fetch origin
.
If you're working on the same branch and you want to update your local branch with the remote one git pull origin <branh_name>
If one have made changes that should get shared:
git add file_path_1 file_path_2 directory_path1 ...
git commit -m "<your brief message>"
git push origin <branch_name>