This has been a challenge for a while. Different web postings say to do different things. This is the way I solve it

This article uses the example of Kargo - a Kubernetes installer

Fork the project

From the Github UI, fork the Kargo project. The new repo will be in called linuxsimba/kargo

Add a Upstream Repo to the Forked project

From CLI type:

cd kargo
git remote add upstream https://github.com/kubernetes-incubator/kargo

Fetch the upstream branches

Update the upstream branches

git fetch upstream

Call the main branch of the upstream repo "upstream_master"

git checkout -b upstream_master --track upstream/master

When upstream is changed

When upstream master branch is updated, this is the steps taken to update the Linuxsimba fork master branch

git checkout upstream_master
git pull upstream master
git checkout master
git merge upstream_master