Space administrators can manage any Project, but Project administrators can help manage certain Projects. Project administrators can be set for each Project.
For details about each role, please refer to User Privileges.
Add Project administrators from the Project Administrator Settings page (Click your profile icon in the top right corner > Space Settings > Project Settings > Project. Then, click the Project in question and select "Project Administrator Settings").
Only administrators can see the "Project Administer Settings" button, but Project administrators might also see it on the Edit Project basic settings page.