You can easily reach Genk by car via the motorways E313 (Hasselt-Liège via the Diepenbeek exit) and E314 (Brussels-Aachen) via exit 31 and 32. You will then quickly reach the center via the Westerring or Europalaan.
From Brussels and Antwerp it barely takes you an hour to Genk.
Genk is located half an hour from Aachen, and 15 minutes from Hasselt or Maastricht.
By public transport
You can take the train to the center of Genk. More info via the website of the NMBS.
Genk is also easy to reach by bus. More info via the website of De Lijn.