Some Tips

After selecting a project, if there is only one Work Item in the project, then it is automatically selected.
After selecting the task, on mouse-over, you will see the following information : Parent, Hours (Est), Hours (Submitted).
By default, only tasks assigned to a user will be displayed in the Task drop-down list. If you want to allow people not assigned on a task to fill time against a task, you can do that by granting them View Project, View Task and Add Time privileges to the appropriate roles.
By default you are taken to the current week on the Weekly Time screen. You can pan back or forward, one week at a time. Alternately you can jump to any specific week by clicking on the pull down arrow next to the week.
If a Work Item you are expecting to view is not listed, do the following:
1. Check that the Work Item matches the filters (click on Filter Work Items...). For more details, refer here.
2. The Work Item may be part of an archived/In Planning project and time entries may be turned off for archived/In-Planning projects.
3. Check with your manager if time is allowed against that Work Item.
4. Check that you are either assigned to the Work Item or that you have view project and view and add time privileges on Work Items not assigned to you.
The % Comp option behavior:
1. The % Complete of a task is updated as soon as you submit the time-entries for Approval (Send For approval). This does not require the time-entries to be approved. You will not see the % Complete you entered after you have submitted the time-entries for approval.
2. The % Comp entered for saved time-entries will not affect the % Complete of the task till such time-entries are Sent for Approval.
3. The %Comp is a convenient way to enter % Complete of the task when filling time. You cannot only enter %Comp against the task; time-entries also need to be made against them for the %Comp to be reflected.