FlashPeak doesn't have support for extensions. It only supports a few plugins since they're based on Internet Explorer. The developers have created SlimJet, which is something like FlashPeak and it's based on Chromium, the engine behind Google Chrome. You might be able to install extensions if you choose this browser instead, but for FlashPeak there won't be support for Google Chrome's extensions, primary because it doesn't run on Chromium.
