You can see an overview of Tasks assigned to you and your colleagues by going to the Manage Tasks page
Steps
Select My Apps
Choose Tasks
You arrive on the Manage Tasks page
From here you can
Edit a Task
Mark a Task as Done
See Done tasks
How to mark a Task as Done
Simply tick the checkbox next to the Task to mark it as Done
How to see Tasks that are Done
You always start off on the To Do tab
Select the Done tab on the Tasks pane
You arrive on the Done tab