You must apply to Systems Support for Gitlab access.
Your gitlab account will be valid while you are a student in CIS, unlike the rest of devweb which is only guaranteed to exist until the start of the next academic year.
Once you have your gitlab account you'll need to create a "New Project" before trying to anything else
Gitlab is accessed over https, (or SSH) with command line tools similar to CVS, or integration with IDEs
The https URIs for Gitlab look like this https://gitlab.cis.strath.ac.uk/username/projectname.git
The SSH URIs for Gitlab look like this ssh://firstname.lastname@example.org:2222/username/projectname.git
SSH access requires that you first set up a SSH key in gitlab!
For more information on GIT please read the GIT Documentation
Please see the CIS FAQ about Mattermost and Gitlab