Hi Shamima,
I'm not exactly sure what you're asking about. What do you mean by you used "DE gene sets"?
If you used the Hallmarks gene sets, then the heatmaps should be on the results page for a given set. If That set didn't generate plots because it wasn't high enough on the ranked list, then it won't have a heatmap. In that case, you can look under advanced fields for the parameter to determine the number of top sets to plot. Increasing that might cause the sets you're interested in to plot.
If that isn't the issue, please send me a screenshot of what you're seeing so I can better understand the issue here.
-Anthony
Anthony S. Castanza, PhD
Curator, Molecular Signatures Database
Mesirov Lab, Department of Medicine
University of California, San Diego