The pressing plate should be sitting inside the mould/basket at the bottom.
Have a look inside, if the base is solid (no holes) then the plate is there inside. You might need turn over the mould/basket and give it a few pats on the base, to dislodge it, so the plate falls out.
If you can see the holes in the base of the mould then your plate is not there and you should contact the store you purchased from or contact us.
For how to use the press see here.