If you remove the glass side panel the SSD mounts are on the right hand side (The 4 rectangle shapes). There should be holes that match up with the holes on the SSD. Just use a short screw for that to fix it in place. With an SSD though you can basically just leave it anywhere as no moving parts so not a big issue. I have a couple in my case that are just hanging from the sata cable.
The hard drive cage is just below it, and you will need to take the other side panel off. Depending on what the system is you might have to screw them in as well. The holes on the sides of the HDD should line up.
The SSD might actually mount at the rear so try both ways.