I need to observe the different modes at different resonant frequencies of my antenna design. Can anyone send*the needful suggestion to observe the modes in simulation softwares HFSS or CST MW studio.
From your question it seems that you have not started using these solvers provided I am getting your question.
In both CST and HFSS it is the same procedure.
Use Eigen mode solver.
Draw your geometry.
Assign the boundaries.
Define proper mesh
Simulate the model and you will get the possible modes