In order to input a generator system of a permutation group, please input a vector consisting of the generators of the permutation group.
In order to enter a vector, first enter '[', then enter the elements of the vector separated by commas, and finally enter ']'. Since the entries of the vector are permutations you must know how to input a permutation.
For instance the generators of the symmetric group S3 of three elements could be entered as [[2,3,1],[2,1,3]]. (All generators must be permutations of the same length!).