I had a slightly older lancer a few years ago.
I might not be very much help as it was a few years ago, but I can see no one else has answered so I'll give it a go.
There were some grey discs behind the head rests that could be removed so the anchor points could be installed (buy at any baby shop than take it to any mechanic/ large servo to install). The discs were about the size of a 10c piece and I could pull them off fairly easy with your nails or keys lol.
Or you could fold down the seats and the anchor points were there at the base (but I think this was actually the hatchback I had prior to the lancer).
Good luck and I hope that helps???