Updating PSP custom firmware 3.10 OE-A to newer version

So i'm currently on PSP custom firmware 3.10 OE-A and I don't understand how to update it, i've read Bizzy's tutorial and that doesn't help me. I also need it to be a custom firmware that plays Crisis Core. Please help if you can, i'm too afraid of messing it up

Edit- It's a PSP Phat

 

Hey cjdogger, please do the following steps:

1) Download 3.90 m33-2: http://dl.qj.net/Custom-Firmware-3.90-M33-update-2-PSP/pg/12/fid/15942/catid/163
2) Download Official firmware (OFW) 3.90: http://www.psp-hacks.com/file/1406
3) extract them both, and place the OFW 3.90 into the UPDATE folder, which is located in the M33 folder.
4) rename the OFW 3.90 to 390.PBP.
5) Place the UPDATE folder into the PSP/GAME folder on your memory stick.
6) Then run it from your psp, follow the onscreen instructions.

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Thanks, Dmac
Those instructions are really clear, I'll do it tomorrow, thanks!