The 'Quick timesheet' feature is available from within requisition type activities. Open the activity that you are working on and click the 'Quick timesheet' button.
This opens a window where you can enter the phase (for a job level activity), charge code, time spent and work done notes. The date defaults to the current day's date. From this window you can change the kanban status on the activity and/or mark the activity as complete. Click 'Post' to enter the timesheet.
Note: You can restrict the creation of quick timesheets from an activity to the activity owner only or allow it for any user. You can also disable this feature. To change these settings go to Settings, File Maintenance, Activity Types. Open the requisition activity type, under 'Can create timesheet' select 'Owner only', 'Anyone' or 'No'.
The Timesheets tab on the activity will only show timesheets created using the quick timesheet function on that activity.