I was thrown off by that too, at first. But if you look in the "latest" directory, you'll find the install packages:
fxp://ftp.simics.net/pub/simics/latest/
It's a weird way to organize things, but they might not intend for people to be browsing the ftp directly
Edit: Oh yeah, more detailed instructions are in their readme:
fxp://ftp.simics.net/pub/simics/README