The pathway to Professional Certification for environmental professionals is simple:

Sign up for the E-Course that corresponds to the Professional Certification you desire.  Complete the entire E-Course curriculum on-line, receive your Course Completion Certificate and then take and pass a set of examinations related to the content of the E-Course you took.  After passing the exams, submit an Application for Certification documenting your educational and employment background in an environmental field.

More detailed information on certification requirements can be found here.