All grids are always in edit mode so the data on any row of any grid can be edited directly by clicking on the cell and typing your edits.
To cancel the edits to the current cell press the [ESCAPE] key. You can cancel all edits on a row by pressing [ESCAPE] a second time.
If you wish to mass update/edit grid items simply select the Bulk Update tab.
Select the field you wish to update and the data to be mass populated and click Save