...
Task & Update Timesheets need to be enabled on each project where you want time to be recorded
Once turned on, users will be prompted to log the Time Spent whenever they
mark a task as done - as long as the task is tagged to that project
post an update within that project
If you also have Cases enabled on your project, you can report on the time spent on each Case.
Steps to turn on Task & Update timesheets
Go to the Project Preferences page and tick the Enable timesheets on this project checkbox
Scroll down and press Save
That’s it, Task & Update timesheets are now enabled