The top of your Inbox displays your availability to receive tasks.
To change your availability to receive tasks:
Click Inbox.
At the top of your Inbox, click one of these:
I am available
I am currently set to unavailable
Do one of these:
To make yourself available, deselect the checkbox that changes your status to unavailable.
To make yourself unavailable, select the checkbox that changes your status to unavailable, then click edit, then select another user to receive your tasks, and then click OK. For detailed steps see Locate an item in a selection dialog box.
When you make yourself unavailable, this only affects future tasks that have been marked as delegable. This option does not affect tasks that are currently in your Inbox or any future tasks that do not allow delegation.