You can restrict project access either 
- when you create a project
- or after it is created

On the dashboard, click on the "Share project" button


Only the team members you select will have access

Open the second dropdown just below to choose who can access this project

Check the names of the team members you want to give access to this project

You can also restrict access to specific team members when you create a new project

After naming your project, you will find a dropdown where you can define how you want you project to be shared. 

And check the name of the team members you want to access this project

How to restrict a project to specific team members