Thanks for the compliment. I'm a real newby compared to many of the folks here on this forum!
Basically you need some tools then, before you can even start a sheath. And of course some leather.
There are a couple newish threads here in this forum by folks asking about tools to get started. If you page down the list a bit, you will likely find them, and that will get you started accumulating tools.
Once you have the tools, you'll need a bit of leather. I get my stuff from Tandy, some folks get theirs elsewhere, but a web search will find you lots of sources.
Once you have the tools and the leather, you can begin, but most sheaths have these basic componants:
1. Body - this is the main part of the sheath which encloses the knife
2. Welt - most sheaths have a welt, which is another layer of leather which runs along the edge of the sheath, more or less wherever there is stitching. This is to help protect the stitching from the edge of the knife.
3. Attachments - by this I mean, whatever the sheathmaker is using to attach the sheath to something else, be it a dangler, a belt loop, whatever.
4. Something to hold the sheath and attachments together - this would include thread, rivets, grommets, glue, etc. These things hold the parts of the sheath together to make a whole.
Before you begin, you should make a fairly detailed plan for how the sheath will look. You will of course need the specific knife, but basic design plans like; how big, how thick the leather will be, what kind of shape you want, attachment style, etc.
Once you decide what the sheath will consist of, you can start to get specific with your plans. I find it helpful to sit down with pencil and paper and actually draw what is in my head. It doesn't matter if you are artistic; I'm not. It just helps to solidify your thoughts.
There are lots of tutorials on line and here on the forums. Take some time to look around and get an idea of how folks do things. Everybody has their own techniques, but the main thing is doing things in an orderly fashion so you don't get ahead of yourself.
Andy