Remove the oval jump ring from the opposite end of the other bracelet and replace with a round jump ring.
Link the sterling frames together with jump rings in a pattern you like, and attach to the two bracelets with the round jump rings you just added. Clasp the bracelets together to complete the necklace.
You will have a sterling silver clasp left over from this to use on another project.
2 each #50-447 Sterling Silver Double Parallel Chain Bracelet, 7.5"
1 each #44-050-73-30 Sterling Silver 11mm Square Frame Link
2 each #44-050-73-31 Sterling Silver 14mm Round Frame Link
2 each #44-050-73-32 Sterling Silver 12mm Triangle Frame Link
1 ten use 6 each #37-295-670 Sterling Silver Jump Ring, Round, 7mm
#69-056 EURO TOOL Side Flush Cutter
#69-275-09 Wubbers Bent Chain-Nose Jewelry Making Pliers
#69-275-03 Wubbers Chain-Nose Jewelry Making Pliers