Take Ownership of Multiple Activities or TasksTake Ownership of Multiple Activities or TasksThe owner of a group of activity or task records is responsible for managing the work associated with those records. You can assign an owner to multiple records or take ownership of them yourself.
On the List tab in the Activities and Tasks (SP) application, click the Select Records check box at the bottom of the page. A Select Record check box opens next to each record on the List tab.
Select the records of which you want to take ownership.
Note: To select a record, click the Select Record check box. To cancel a selection, clear the check box. To select all records in the result set, select the check box next to the column header.
From the Select
Action menu, select Take Ownership,
or in the Toolbar, click Take Ownership 
to
open the Take Ownership dialog box.
The system assigns the logged in user as the owner and the status of the selected records changes to QUEUED. (The exception to this occurs if the status is RESOLVED; in such a case, the status does not change.)
Assign Owner to Multiple Activities