You can take the M2 Yenikapı-Hacıosman metro line and get off at Osmanbey or Taksim stations to easily access Istanbul Congress Center.
Osmanbey and Taksim metro stations are approximately 7 minutes’ walking distance to Istanbul Congress Center.
Alternatively, you can use the F1 Taksim - Kabataş funicular line and get off at Taksim station to reach to Istanbul Congress Center.