Note that posting feedback is a compulsory step before completing the task.

Steps:

1. Log into the system
2. At the top right corner of the page locate and click on the notification icon (represented by a bell like feature) at the top right of the page
3. Click on My to do list from the presented options. This directs to a page displaying all your tasks
4. Go to the specific task you wish to complete and click on the View link. Post feedback and select the appropriate receivers (this step is compulsory before completing a task)
5. Return to your to do list, click on the check box at the far right of the task you wish to complete 
6. Scroll down to the bottom page, on the bulk Action drop down select Complete the click on Go to compete the action.