Lst = {3, 4, 5, 6}
->{3, 4, 5, 6}

PrependTo[ Lst, 2]
->{2, 3, 4, 5, 6}
PrependTo[ Lst, 1]
->{1, 2, 3, 4, 5, 6}

Lst
->{1, 2, 3, 4, 5, 6}

Insert[ Lst, X, 4]
->{1, 2, 3, X, 4, 5, 6}