After going into repo, on the left side there is a menu, 5th position is Requirements, we can create list posiotions.
My question is how/where project is checked against requirements?
The requirement IDs can be referenced in CI Jobs through use of a JSON file output described at Requirements Management | GitLab
It is currently a little manual (it is not magically interpreted as a rule - it is provided as a management feature instead currently). Your test phase (or other stages) will need to produce the specific JSON format output as a file, with each key-value representing a requirement identifier, and mark the file created as a requirement artifact to allow the checker to receive, understand, and process the file against the list of available requirements.
It may also be of help to read the motivation and perceived use-cases behind the feature here: Trace Requirements to Tests (&2859) · Epics · GitLab.org · GitLab
Still understand nothing