Stock folding system will look something like this...
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You will need these tools. Two 5mm allen key or wrenches depending on your bolt of choice. Three rear B axles, or 3 half inch axles, and a flathead screwdriver.
Use the flathead screwdriver to remove the C clips that hold the folding mech axles in place. Put it under one of the sides and push it up (towards you). it will pop off fast, so be careful.
Once you have done this, remove the axles. These axles are attached to prings within the folding mech. So be sure to rip it out or use the flathead screw driver to stretch the spring out.
Once you have gutted the folding system this is all that you should have removed.
This is what the inside of your folding mech should look like once gutted.
Once you have done all of this, just slip the axles in through these areas. Depending on the axle, you may need spacers. I find that sometimes you don't have them, and old bearings work real well. I don't usually go out buying spacers so this is a good resort. Once tightened down enough the bearing wont spin and your folding system shouldnt move. I recommend a half inch axle to go through the folding system as shown. It clamps it a lot more than a B axle so it's much more reliable.
Pretty much self explanitory, common sense on how it works.