help not understanding how to solve this problem:

1. Give a BNF grammar for each of the languages below. For example, a correct answer for the set of all strings consisting of zero or more concatenated copies of the string ab would be this grammar:

::= ab |

1. The set of all strings consisting of an open bracket (the symbol [ ) followed by a list of one or more digits separated by commas, followed by a closing bracket (the symbol ] ).