Regarding your first comment, a user must have administrative access to be able to log time for projects, tasks, and issues in the Hours section. There's more information about that in the "Project, task, or issue - Hours Section" on this page: Documentation > Workfront > Workfront Guide > Log time.
If you just need your users to be able to log time at the Project-Level (within Timesheets), two things must happen:
1. In Setup > Timesheets & Hours > Preferences, you must have "Directly on projects" selected in the "Where users can log time" section.
2. The person/role/team/group needs to have the access "Contribute - Log Hours" turned on for the project (when you select the "Share" button for a project). You can also set this at the template level.
Contribute - Log Hours menu in the Share settings