Where can I download the game?, Or is it simply downloading the dlc?

you can find some psp roms on Vimm's Lair. I doubt the DLC is there though...

It won't let me enter the page

I would message @mican8s directly in the discord.

The PSP ROM file for the game you have to find online. But for the DLC files I have provided a link to the archive.org page under "Link to DLC files"