Where to exit
Take the train to Cologne Central Station (Köln HBF) or Köln Deutz/Messe. There are several cheap rates offered by Die Bahn: e.g. the Schöner-Tag-Ticket (25 for 5 persons, but only inside NRW, and only on work-days), the Mitfahrerrabatt (drive in groups up to five persons, where everyone except the first person will pay half of the regular price, only) or even cheaper prices for larger groups. If you're planning to come via train from abroad, simply check the homepage of your national train company.
How to get to the partyplace
From Köln HBF
There is a connection via Neumarkt to reach the Evoke location. More information here.
From Köln Deutz/Messe
More information on this connection here.