All I did was the steps in the ReadMe basically, if you have any specific questions on a Step Number, then post them and I will help you further.
1) Extract Street_Fighter_Alpha_3_MAX_USA_PSP-ARTiSAN iSO to a folder on your PC using iSOBuster or similar utility.
2) Outside of PSP_GAME is a UMD_DATA.BIN file, delete this. Inside of PSP_GAME are ICON0.PNG, PARAM.SFO, and PIC1.PNG so move these to the root of the SFALPHA3 folder in this package.
3) In your original PSP_GAME\SYSDIR move the UPDATE folder to SFALPHA3\SYSDIR in the pack folder. Ignore or delete the BOOT.BIN and EBOOT.BIN files remaining in the original PSP_GAME\SYSDIR folder as there is already a new BOOT.BIN and PATCHED_BOOT.BIN in the pack SFALPHA3\SYSDIR.
4) In your original PSP_GAME\USRDIR delete the dummy.bin file, and move the usa folder into the new SFALPHA3\USRDIR folder from this pack.
5) Now follow the instructions as normal from the included NFO file:
Copy the 3 folders to your Memory Stick, boot RunUMD.
Press X (do not hit O to extract update).
The game will load if you did everything correct!