CFW Pro C2: http://www.mediafire.com/file/84hq07calk938qw/6.61_PRO-C2_22-01-2015_%281%29.zip
OFW 6.61: https://www.playstation.com/en-us/support/system-updates/psp/
Step 1: After Downloading the files from above, I gave the actual link to the Sony Software because each one is different for certain models, You can install the 6.61 OFW first if your not running it already.
Step 2: Skip to Step 3 if you already have this installed, On your PSP Copy your EBOOT.PBP to the PSP/GAME/UPDATE folder. Navigate to your game section on your XMB and load the update.
Step 3: Once your running 6.61 OFW, you can now extract your files from the 6.61 PRO-C2_22-01-2015 (1).ZIP and you will see the following folders: PSP and seplugins, ignore the seplugins folder and navigate through the PSP folder and you will see a GAME folder open that and these are the files we will be looking at.
(For PSP 1000 & 2000 models!!)
Put your PSP into USB mode on on the Root of your System Storage/Memory Stick navigate to PSP/GAME folder, Copy the PROUPDATE & CIPL_Flasher to your GAME folder.
(For PSP 3000, Go & E1000!!)
On the root of your System Storage/Memory Stick, navigate to your PSP/GAME folder and copy the PROUPDATE and FastRecovery folder to your GAME folder
Step 5: Once you've copied over the files, exit USB mode and navigate on your PSP to your Game section on the XMB and Run the PRO Update, Follow the instructions on screen and install the firmware.
(PSP 1000 & 2000 models)
Run your CIPL Flasher to Permanently install the CFW 6.61 PRO C2
(PSP 3000, Go, E1000)
Run Fast Recovery to "SaveState" your PSP so if you ever need to reboot or your battery dies you can just run Fast Recovery to be back up and running.