How do I mount these loooog springs to my Toyota?
You must get a new front spring hanger and weld it on the flat part of the frame forward of the stock spring hanger.
For the rear shackle hanger, you can either go with a double shackle set-up (very popular) or weld on a new hanger back about 4 inches from stock.

Where do I get new front spring hangers?
You can either buy Jeep CJ spring hangers (some say they hang kinda low) or make your own out of 3.5" x 3.5" x 1/4" or 3/16" square tube.
You can't use the chevy front hangers they are shaped to oddly to work.

Can you explain the double shackle set-up?
Ok the double shackle set-up works like this. You connect one Toyota style shackle from the factory rear hanger (let it lay flat against the frame)
to another shackle going straight down to the spring. Most people run the stock Chevy shackle as the second one that mounts to the spring. Or you can make your own shackles.
Doing the double shackle set-up is just a cheaper and easier way to do the rear of the springs. No need to weld in a new hanger. It also gives you a bunch of extra suspension droop, which is a good thing!