I am relatively new to git. Our organization uses a Fork & Pull Model for managing changes to the master branch. Each developer forks the master and branches from their fork
You first need to add the other developer repository as a remote.
git remote add otherrep uriToOtherRep
Then you fetch changes from there
git fetch otherrep
And then you merge the branch from the remote repository into yours
git merge otherrep/branchname
Happy merging!