OleDbConnection baglanti;
baglanti=new OleDbConnection("provider=microsoft.ace.oledb.12.0; data source=c:\\users\\taha\\desktop\\db.accdb")
baglanti.Open();
OleDbCommand ekle=new OleDbCommand("insert into uyeler (kullaniciAdi) values(txtKullaniciAdi.Text)",baglanti);
ekle.executeNonQuery()...