Install all those VST plugins in the same folder.
To make it easy on you, install or copy the .dll files to this folder path:
BTW, This folder path is for FL Studio 6. It's the same concept though for the older versions, just get those files into that last VST folder.
OK, then once you have them all in that folder, go open up FL Studio, go to the "Channels" menu at the top, then go to "Add one," then click on "More...," then when that white retangular box pops up go down to the bottom and click on the "Refresh" button, then click on "Fast Scan (recommended)." Then once it finishes looking for new plugins, it will say it found X number of new plugins, then just search for them in that list (they will be in red color) and select the little boxes to activate them, then close down that retangular box. Go back to the Channels menu and all the new plugins should be there in that list.
Do same steps for FX plugins. Hope this helps.