hmmm...well you can't do much. "Decrypted" means that people who do have a homebrew-compatible PSP can emulate it (use it without permanently having it). I'm sorry, but until a 3.11 Downgrader is released, you will not be able to use homebrew.
However, there are loads of free Flash applications and games you can enjoy in the mean time here:
http://psp-news.dcemu.co.uk/psp-flash-homebrew.shtml
To start, I would recommend a "portal," qhich contains many games and stuff bundled into it, such as "ICP Phlash Portal" (my own), pspWxp, or X5. JJust google these.
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