UPDATED: Another way is to install using docker, see here
GitLab packages (beta) These packages contain GitLab and all its depencies (PostgreSQL, Redis, Nginx, Unicorn, etc.). They are made with omnibus-gitlab that also contains the installation instructions. These packages currently support a reduced selection of GitLab’s normal features. For instance, it is not yet possible to create/restore application backups or to use HTTPS.
GitLab virtual machine images contain an operating system and a preinstalled GitLab. They are made with GitLab Packer that also contains the installation instructions.
After the steps below your GitLab instance should reachable over HTTP, and have an admin user with username root and password 5iveL!fe.