I downloaded waves demo on my computer and updated the plugins in Cubase.
The plugin (debreath) is already there but nothing showed up when I pressed on it.
My computer is running on 32 bit but official site says the softwares are of 64 bit.
Interestingly, I could open DeEsser (also a 64 software) without problem. Why is that?
Waves are both 64 bit and 32bit. You need to make sure you only install the 32bit if you are using 32bit windows.
http://www.waves.com/plugins/debreath#removing-vocal-breaths-with-debreath
I download the plugin from this page, but I can’t find there is 32 bit version 
anyone?
Make sure that waveshell.dll is in a location that Cubase is scanning for plugs.
The actual plugin dll should be somewhere that Cubase isn’t looking.
You should get asked for locations for 32 or 64bit during the install and then you could be sure you weren’t trying to use the 64bit which can’t work.
The whole waves package is usually installed into c/program files 86 and just the 64 bit dll’s are place into 64 bit vst plugin folder. As long as you don’t get the licence missing errors when you run cubase you should be able to update/rescan the vst folder paths from the plugin manager and find them.