Probably about the easiest and less painless way is set yourself up a VM, and then follow the install guide here: Download and install GitLab | GitLab
Choose the appropriate distro that you’ve created the VM with and then follow the few steps that are there to get you running. All other stuff is very well documented here: https://docs.gitlab.com/
Whether you prefer docker or kubernetes/openshift to run it on instead is up to you. I find it far less painful and easier to maintain via a VM than run it in a container. But that’s just my personal preference. Others may disagree