I use forceps (medical ones that I picked up from a medical suppliers) but any pointed nose pliers will do the trick, tweezers won’t work as they are not strong enough. I use cheap silver plated jump rings and chain which I get from the jewellery section in Hobbycraft but I would think you could pick these supplies up at any bead/craft store.
Hold the jump ring with both sets of forceps/pliers with the join uppermost.
Twist the right hand forceps/pliers towards you – DO NOT PULL IT OUTWARDS, all this does is misshape the jump ring, By twisting it forwards to open and backwards to close the ring remains a perfect circle and does not distort.
Repeat with the other end of the chain and feed this jump ring on to the brad to secure to your flower.
Thanks for looking,