well, here is the steps

In FX, click menu Tools-->Add-ons-->type in "flash block" in the 'Get Add-ons" tap--> install it by clicking "add to firefox". Same way to find and install adblock plus. Once restarting the firefox, ABP will ask you to subscribe a list, usually the Chinalist, or easyUS list.

The blockers will block many pop ups and flash type of links. However, it can't prevent everything if you really want to get infected. Flashblock will show a big F when it is blocking, so don't click it to unlock unless it is a known site.

If every flash is blocked, many good sites such as youtube will be blocked as well. ... so life is complicated.