Redmine records work hours through a project module named Time tracking. Enable it when a project needs spent-time totals, activity-based reports, or a Log time form for issue and project work.
The module is controlled from the project settings page. When it is disabled, issue tracking can still work, but the project overview does not show the Time tracking panel and users cannot open the project Log time form.
Project activities come from Redmine time tracking enumerations and can be narrowed per project. Keep only the activities that match the team's reporting categories, then confirm the Log time form offers the intended activity before handing the project to users.
Related: How to create a Redmine project
Related: How to log time in Redmine
Activity names are managed under Administration → Enumerations. The project tab only enables or disables existing activities for this project.
Users who record entries need a role with Log spent time permission.
Related: How to set Redmine role permissions