Step 1: Get yer stuff!
-military boots (or other boots that could be transformed into pirate boots)
-leather (sorry, I don't know how and where you can buy leather since I have a box full of leather sheet. I checked a bit on the internet and the price really varies depending of the leather quality and/or the quantity. But I'm squarely sure that won't cost an arm.)
-A sewing kit (thus including needles (you'll need BIG needles to sew leather, seriously I just broke one regular needle by doing this), thread (black thread fits well the leather than white/clear thread), scissors and a thimble (be careful if like me you're using a cheap plastic-made thimble, the back of the needle can perfectly well puncture the thimble and your thumb both while sewing leather))
And to attach the covering: