WL's clunky interface is one of the reasons I use Adobe Audition. Anyway, I'm guessing what you're looking for is roughly:
Analysis | 3D Frequency Analysis
or
Analysis | Spectrum Analyzer or Meter (neither of which I could get to actually do anything just now)
Then, after getting an idea of where the hiss falls in the frequency spectrum, turn on the "Mastering Section": Options | Use Mastering Section and try one or both of the following tools:
VST | DeNoiser
VST | Q
"Play" your file to hear the impact of the functions, and Render to apply them. To be honest, I don't recall now if the VST's above came standard, or if I added them later.
I've tried and not found something as effective or as simple to use as AA's Noise Reduction utility with which one may take a snapshot of the noise (e.g. record a few seconds of nothing but blank tape) and then "remove" the noise using the analysis of the snapshot. The key here is the settings are very configurable and customizable - the user has complete control over how much to trust the analysis, customize the frequencies targeted, establish how much to take out, whether to do it in one fell swoop or apply multiple minimum-impact passes, etc. Takes an awful lot of fiddling to get it right, and less fiddling is more, if you know what I mean. But it's worked fairly well for me in the past. The Fs analysis and parametric EQ in AA also works well for this sorta thing. Anyway, none of that helps you...sorry for the ramble.