Effective microorganisms mother culture can be used straight from the bottle, or it can be activated first.
Note that EM is sold under many brand names (you may have searched for em1, em-1, emro, biosa, efficient microbes, etc.) some better than others.
This one from SCD called 'ProBio Balance Plus' is on par with the best of them, made by people who have studied under Dr. Teruo Higa.