Hi @cecilia,
Welcome to Atlassian Community!
Yes, this is possible. What you have to do is change the permission scheme(s) that your current projects are using so only users belonging to a specific group or project role can browse the project, I would recommend using project roles, you can then control it based on the project instead of having to have multiple groups. You can then add the people that should only access to the one project to that role. You can find more information about how permissions works here, How do Jira permissions work?
I see your question is marked under Jeera service management. As such my first question is are you looking to add a customer or an agent? In either case when you add a user you add them to the application but you can also limit access to a single project. this is all managed via roles, groups in project permissions.
You must be a registered user to add a comment. If you've already registered, sign in. Otherwise, register and sign in.
You must be a registered user to add a comment. If you've already registered, sign in. Otherwise, register and sign in.