If you were lucky enough to Grab UNO before it was taken down then you will want to check out the initial release fo the ARK UNO 2.00-2.02 eCFW.  And show some love to the developers who put in a lot of hard work and time for something for us all to enjoy.  ARK is the PSP eCFW that you want.  You'll be able to take advantage of a lot of PSP Homebrew and other stuff thatnks to the support ARK eCFW provides.

The list of featues is quite impressive.  Some include support for your PSX games, a customizable menu, plugin support and a lot more which can be found at the source link.

Here are the instructions but before you begin anything make sure that you go to the source link for a full list of instructions, warnings and tips so nothing gets screwed up.

"ARK is a PSP Emulator Custom Firmware for your Vita. It supports most PSP Homebrews, plugins, and backups, as well as PS1 games

Instructions :
> Go into the ARK folder
> Choose your region and copy the savedata to your 'PS VitaPSAVEDATAXXXXXXXXXXXXXXXX' folder
> Transfer it to your PSVita using CMA"

Also make sure you check out the paypal link for the developers.  Donations by nature aren't required but these talented guys did a ton of great work and it would be awesome to show them some love.

Source