The holy grail of PSP hacking. Look for the "Themes, Wallpapers, and Customization" subforum. They have a pinned thread called "CTF Repository."
Search for "CTF Theme Pack" in the PSP section. Users constantly re-upload dead links. You will find MEGA.nz links here that are still active as of 2025. psp ctf theme pack 660 link
You can find several curated collections of 6.60-compatible CTF themes through these community-maintained sources: The holy grail of PSP hacking
Unfortunately, without a specific link provided in your query, I can only give a general guide on how to approach installing a CTF theme pack on a PSP running firmware 6.60: psp ctf theme pack 660 link