The instructions on Maxscript website are pretty self explanatory: first select the type of material you want to work on (CoronaLegacyMtl, CoronaPhysicalMtl ...), then select whta materials you want to work on (materials of selected objects, Medit selection ... beware the script doesn't seem to work with SME), and finally, in your case, you want to select "Map - texmapFresnelIor" (if I'm not wrong, please double check) and select "Clear map slot" at the bottom of the script UI so that you will delete all maps plugged into the FresnelIor map slot for the given materials.
Please double check what I say, and save your work before proceeding as this operation is undoable and I could possibly have misunderstood your query.
