Happy Friday everyone 
Me and my wife are going through a great spell of sex at the moment
my wife dropped a hint the other day of using silk/satin for a bit of light bondage while having sex, so this arrived as a surprise for her
We have handcuffs that she loves me to use on her, which are easy to use. But how do you use these, I can’t see how you would use one for the wrists and one for the ankles. We don’t want to tie them to anything???
I don’t have those particular ones and the product imagery isn’t great, but most satin ties aren’t designed to tie both wrists or ankles together with one tie. You would need to put one on each wrist and then tie the two ends together
I suggest you’d be better with under-bed restraints if you want to tie to “something”. We use these and they’re great.
Hey @FD1 , glad you’re having so much fun, and is even better when you’re both willing to try new things.
We dont have the satin ones either, but as suggested by @Tryanything, we do have the Bondage Boutique Bound to Please Under-Mattress Restraints and to be honest, these are really comfy to wear, and also tuck away really discreetly. But lets us know what the satin ones are like if you do try, be very interested. 
Hey @FD1 , satin scarfs are great but they also have their limitations - namely, you need to know your knots before you use them.
The way I’ve always used them is to wrap them twice around the wrists from the centre then once ove the middle, creatign a kind of wrist binder/cuff thing. With the ends, knot them with square knot (you can find tutorials on Google) or a bow. Do not use a double knot! You want to be able to undo it quickly in the event of an emergency, though really I waund encourage you to have a pair of bandage scissors on hand, just to be extra sure. Have fun! 
Happy days! Sounds like your both in for a great weekend 