Some code would be nice.
I would say that you don't edit the datagridview directly. You bind a datatable to it.
If you insist:
dataGridView1.Rows.Add(new object[]{11, "Some text", DateTime.Now, 33});
dataGridView1.Rows[0].Cells[1].Value = "Some other text";
dataGridView1.Rows[0].Cells["Column3"].Value = DateTime.UtcNow;
BTW. As datagridveiw is not available in WPF, I don't understand why you have tagged this with WPF.