Vb.net - how do I add a row in a datagridview to an existing object?

vb.net - how do I add a row in a datagridview to an existing object?

If I load a form and populate the obj the above is fine
I need to add an extra line(s) manually, say either with textbox controls or other vars

me.datagridview_1.rows.add("ColumnName",stringvalue)
or 
me.datagridview_1.rows.add(string1, string2,string3)