I'll try to explain, though it is a bit difficult without having hands-on.
Single Rocket Pouch
1. Lay the yoke on the floor with the straps spread as shown in the picture.
2. Place the Rocket Pouch on top of the yoke with the zip end at the top.
3. Fit the inner shoulder clips of the yoke into the clips at the top of the Rocket Pouch.
4. Turn the whole lot over.
5. The straps that fit onto the front shoulders of the yoke may not be attached or they may have been attached wrongly. The clip that is part way along the strap (and has a loose length of strap running through it) fits into the clip at the end of the front shoulder pad with the loose length of strap exiting from the uppermost part of the buckle.
6. Making sure that the straps aren't twisted, connect the clips that are at the end of the straps into the clips at the bottom of the Rocket Pouch.
7. Thread the belt part of the yoke through the loops on the part of the Rocket Pouch that rests against your back.
8. Adjust buckles to suit.
Double Rocket Pouch
1. Lay the yoke on the floor with the straps spread as shown in the picture.
2. Zip the Rocket Pouches together. (Once!

)
3. Place the Rocket Pouches on top of the yoke with the zip-opening end at the top.
3. Fit the inner shoulder clips of the yoke into the inner clips at the top of the Rocket Pouches.
4. Fit the outer shoulder clips of the yoke onto the outer clips of the Rocket Pouches.
5. Turn the whole lot over.
6. Fit the clips on the bottom of the yoke mesh panel into the two inner clips at the bottom of the Rocket Pouches.
7. The straps that fit onto the front shoulders of the yoke may not be attached or they may have been attached wrongly. The clip that is part way along the strap (and has a loose length of strap running through it) fits into the clip at the end of the front shoulder pad with the loose length of strap exiting from the uppermost part of the buckle.
8. Making sure that the straps aren't twisted, connect the clips that are at the end of the straps into the remaining (outer) clips at the bottom of the Rocket Pouch.
9. Thread the belt part of the yoke through the loops on the part of the Rocket Pouch that rests against your back. Each half of the belt will go through two loops.
10. Adjust buckles to suit.
With both fittings, there are ways that you can further attach this lot to your webbing/belt, but as w-o-t-w says, it's not worth bothering with.
Now thinking, I must have missed off some important bit.....