The case comes with a user’s manual and fasteners:
I was at first bewildered at the lack of rails for optical drives, but recollecting the family connections of this system case I soon found them:
They were at the back side of the faceplate of a 5.25” bay. They are fastened to the drive in the traditional way, i.e. with a screwdriver:
Then you just insert the optical drive into an empty bay:
Note that you don’t have to dismantle the front panel to perform the installation.