hi guys i need some help if anyone can

i populate datagridview1 with an sql query and datagridview2 with another sql query. i have to select a row from datagridview1 and on button1 click to pass the row at datagrid2 and the same for datagridview2. select a row from datagrid2 and on button2 click to pass the row at datagridview1

i have no idea how to do this, i welcome any help