The holder of a standard essential patent (SEP) should first notify the alleged infringer of the SEP, following which the alleged infringer should inform the patent holder of its willingness to take a licence. Then, said licence needs to be offered on FRAND terms.
These steps are guidelines for good faith negotiations between the parties. The term non-discriminatory does not mean that licence conditions should be standard; it may be that specific circumstances necessitate different licence conditions.
Read the full article by Bart van Wezenbeek on Kluwer IP Law.