OK memory refreshed
I'm guessing that you didn't remove the old panel, that why you're asking, the evidence points towards the rust that has formed where the fitting edges have been cleaned up, and then left to rust again!
The front X member that runs from one side to the other, is the main bearer of the front panel, and has upper and lower fitting edges, fit your new panel so that the bottom edge is directly and centrally located over the X member, also bolting the wing bottoms to the front panel will reassure you that you have the new panel is in something like the right place... the rest of the new panel simply overlaps the bottoms of the headlamp panels, and the bonnet lock support panel (slam panel)
Once you're happy with the fit, you can mark the new panel where you want to mount it to the X member, then drill 6mm holes across the upper and lower fitting edges, these holes can then be plug welded with a MIG. Overlap joints should be welded with a series of overlapping tack welds.
Where the the new panel fits over the chassis legs, (square holes) iirc there is a gap between the old and new panels, that should be there, except for one tab on each side, look for evidence of prior welding to confirm
Before fitting the new panel, make sure that all edges are clean, and free from rust, also that the edges are straight...
Wings are only bolted to the front panel, and not welded!
Cleaned edges should be treated with a Zinc coat before welding, pretty sure that this is available from the likes of Halfords, or any Motor factor
HTH
Thom
