Decrypting BBS files: (Needed step to patch the files)
1- Open dnas_installer.exe and choose to install the dnas_decrypter. Then select your PSP drive unit, in this case your Memory Stick or PSP Go HDD.
2- Using UMDGen, open your Birth by Sleep Final Mix iso and navigate to PSP_GAME\USRDIR. Extract BBS0.dat, BBS1.dat, BBS2.dat and BBS3.dat from PSP_GAME\USRDIR\ (Right Click>Extract Selected...)
3- Place ONLY BBS1/2/3 in your memory stick root. Keep BBS0 on your computer for later.
4- Go to your PSP's XMB and run the dnas_decrypter. Don't panic, the screen should stay black for like 10 minutes. If it doesn't stay black for a while and you get 0kb files, it means you didn't have enough space in your MS to decrypt them.
5- You should now have in your memory stick's root your decrypted BBS files  with "_DEC" in the name. Copy them somewhere else and remove the "_DEC" part from the name to continue to with the patching.

************************************************************************************

Patching method:
1- Place BBS0/1/2/3.dat files in the same folder as the BBS Patcher.exe. BSS0.dat should be the file you extracted directly from the iso, while BBS1/2/3.dat should be the files you just decrypted and renamed earlier.
2- Double click "BBS Patcher.exe". If you did everything properly some text should appear telling you the game is being patched.
3- Use UMDGen again to open the ISO and replace the old BBS0/1/2/3.dat files with the new patched ones. Also, change the EBOOT.BIN in the PSP_GAME\SYSDIR folder (not the one in the UPDATE folder) with the one inside the "EXTRA" folder included with the patcher. 
4- After you've replaced the four BBS files and the EBOOT.BIN in UMDGen, click the save button and save as an .iso. Save it with a different name than your original iso.