Two things you are going to need:
A source of regulated dry air. It will probably cost more than your airbrush, but is just as important.
Practice. I would suggest ink on paper towels first, then paint of your choice on junk plastic, something like empty bottles.
Good luck with it. I've seen really nice work done with external mix brushes, but there is some skill involved.
You will no doubt be advised that you should really get a brand X gravity fed internal mix airbrush instead. If you want reviews of some lower priced brushes, check out my website.
Don