Before we start just a note on the tools you can use to attach the metal snap prong buttons. Not everyone will have the special eyelet/prong pliers that I prefer to use so I will walk you through the simple method using plain old pliers. If you prefer to use the special tool that comes with most button kits then please follow the instructions on the back of the package it came with, as I am HORRIBLE with this and cannot help you. I can never align the parts properly and have wasted many a stud button and bruised many fingers in the process.
What you will need to do
The first few steps of this tutorial refer directly to placing a metal snap prong button into the Sandi ID Wallet. (http://www.cutoutandkeep.net/projects/the-sandi-id-wallet-tutorial)
First things first, pop a pin through all the layers of the wallet to mark where you want your button to go.
As you pull the needle out through the layers mark one spot on the wallet and another spot on the top flap. You will have marked two spots on the outer fabric.
You will need to have the right side of the fabric facing up, and push the coloured metal cap (top prong) through the fabric and pierce it - so that the prongs stick through into the wrong side of the fabric.
The coloured metal cap (top prong) should be centered around the mark you left on the fabric. For the Sandi ID wallet, the top prong and stud should be place on the top flap. Whilst the bottom prong and socket should be placed on the base of the wallet.
Focus on the coloured metal cap (top prong) which has pierced through the good side of the fabric on the left. The dark pink cap is there for reference.
Now grab the bottom prong and the socket.
The socket has two sides so the one on the right is how you want it to be placed, otherwise the stud and socket will be a little loose. If you are unsure just snap them to each other and memorise which side of the socket fit - I do it frequently and then forget which side was correct and end up triple checking the fit like a minor OCD habit.