Sodium nitrate is not a ctb method. It's sodium nitrite.
There's tons of information on the site about SN, sodium nitrite. The best place to start is the pinned Resources Compilation, where you'll find Stan's Guide, which thoroughly explains the method, as well as the SN FAQ. There's also a link to a copy of the PPH, but there's no guarantee that it is the original.
I know it might seem difficult at first to get the information, that's why I gave you the most basic resources. If you can read Stan's Guide, which is not very long, then you'll have a good foundation, which is better than relying on people you don't know to instruct you how to do it, that's putting your well-being in the hands of someone who you don't know if you can trust.