If you are using Github Desktop or another desktop app, it may not automatically show the Saudi ADHD Society repositories in your repository list. If so, you need to go to Account Setting --> Integrations --> Applications --> Authorized OAuth Apps --> then Click on "The GitHub Desktop Development App" (or the name of your app) --> Under Organization access grant access (if admin) or send a request for the admin to grant access.
To access the Saudi ADHD Society's private Github repositories from the command line, you have several options, depending on whether you prefer to use Github CLI (gh) or prefer to stick with native git, as well as depending on whether you mind authenticating every time you use it or prefer to cache your credentials securely. See instructions
See Github's git cheatsheet in English or in Arabic.