Heya Mate, hopefully it's not too late - although better if you already had it figured out and installed
Depending on which plate you got will obviously depending on where it bolts up to. Some are longer than others.
I remember when I did mine(4 years ago now) it wasn't always as simple as follow the steps. There was pieces on my car that weren't shown in the instructions.
If you align the plate holes roughly with the cross members on your car you'll have a reasonable idea on where they bolt to. Wiggling a nut, welded to some wire, into the cross member tightened the bolt.
One thing to seriously consider is spacing the plate down 10mm~ away from your oil sump-Long story but trust me
If your still stuck, post up a photo or two of the plate and we'll go from there