We have already discussed on “Selecting multiple records in grid using checkboxes” in our Knowledge base documentation. So please refer the below link for adding checkboxes to grid.
Knowledge Base Link: http://www.syncfusion.com/kb/3180/how-to-perform-multiple-row-selection-using-checkbox-in-a-grid
Please get back to us if you need any further assistance.
Regards
Ragavee U S