It's fairly easy.
I added the inner chains and it still sucks as a target.
The inner chains just make it a more consistent sucky target.
So don't worry that adding chains will turn it into a putter-swallowing monster.
Anyways, like I said, it is easy.
If it's like my Instep,
Measure the length of chain that you want (about 23") and go Lowe's or Home Depot and ask for them to cut 7 of them for you. You'll need to figure out what kind of chain you want. Lighter links will make a tougher target, heavier links will improve the catching efficiency.
Don't worry about the S-hooks, just use cable-ties. You can use S-hooks if you want, but the cable ties make it much easier. You might have to replace the cable ties once a year, if that often.
just secure the top of the chains to the inner ring on the top assembly and connect the bottom of the chains to the bottom chain ring.
Doubling the number of inner chains to 14 will also dramatically improve the catching efficiency.
PM me if you have questions.