How to increase heap size in jme

Hi everyone! i keep getting a lang…Buffer OutOfMemoryException each time i create terrain in the scene composer,or open an image>3mb in the material editor ,and upon restarting ,i can load my image but i dont always get to see the terrain in the scene composer as the error persists at times.I heard about the jmonkeyplatform.conf file ,now i dont know what to change.

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Thaanx for the feedback