Never fall for these - never download flash except directly from http://getflash.com or Adobe or Apple.
That you fell for a common ploy, a scam, duped into downloading malware.
Okay, now how to remove it?
Nuke it.
Restore from backup. You do keep a backup of your system, hopefully a clone in fact.
Assuming you didn't stumble into this forum by accident and have a laptop instead, you do have 65 lb Mac sitting there? Pull the hard drive, slap in a backup or new drive.
Don't use that system.
Use Mountain Lion? use Recovery Mode.
None of that an option? ML does have Gatekeeper.
There are people that keep tabs and posting FAQs and "More like this" on the right side of this page has some common threads. Thomas Reed is active here and Mac OS forum and elsewhere with tutorials and what currently is best.
So going to #2 "malware" thread on the right turns up:
See Thomas Reed's Mac Malware Guide.