Welcome to the Forums! You should probably take a look at this thread to get you started:
beginners-before-posting-your-question- ... 11581.html
As far as your specific question, as you've read, only mineral-free water should be used. So rain, distilled or R/O (reverse osmosis) water is needed. Most bottled water has disolved minerals in it - if it doesn't start off with minerals, they're added for taste - so best to ovoid it. I assume that clean, melted snow should be fine, it just blinged-up rainwater after all.
If you find rain, snow and/or distilled water hard to come by and are nowhere near ready for a R/O setup, another inexpensive choice is a ZeroWater water pitcher set (not other brands, they don't remove all the disolved minerals).
Good luck!
As Robin Hood examined the small bag of plunder, he learned a Life Lesson: Never steal from the rich when they’re out walking the dog.