I mean so that I can view sites that are Flash enabled.
Like the way you would normaly install flash player for IE on your desktop PC to view flash sites.
Macromedia has flash for pocket pc. You can get it here: http://www.macromedia.com/software/flashplayer/pocketpc/2002.html I don't know if its wm5 compatible, but it works great on wm2003se.
I have it on my x51v wm5. You have to download this thing called Macromedia ActiveX (might have flash somewhere in the title) im not sure if what spunker said is it, but it has ActiveX in the title.