Are you serious, you searched the net for how long? 10 seconds?
Whatever....
Their are two ways of obtaining high purity nitric acid, one is to obtain a nitrate salt and mix it with an equal mass of sulfuric acid, then distilling this over to get around 91-95% purity, this is detailed a significant amount on the web and you should have no trouble finding it in either a text form or a video format(YOUTUBE), the only problem is having a distilling apparatus which apparently you do not have along with the experience to have any inkling on how to make such a simple chemical which basically means you should NOT be doing this reaction as you will, almost certainly, hurt yourself.
If your going to be dumb you better be tough(or at least try less dangerous things till you create a chemical so goddamn dangerous)
The second way of producing high purity(up to 98%) is to take already made nitric acid wether it be 68% or 92% and to mix it with an amount of either magnesium nitrate(recommended as in my experience it is significantly cheaper than sulfuric acid) or sulfuric acid, I will leave the exact amount up to you to figure out. The purpose of this is to remove the azeotrope(don't know what that is, DON'T do this) that is formed when you reach a 68% purity, this is done by the dehydration of the water in the azeotrope. Then you take this and distill it over, the only problem is that to reach a 98% purity you have to distill under a vacuum to keep down the decomposition of nitric acid into NO2 as this will contaminate your product, however you can still reach around a 96% purity without a vacuum as long as you control the temperature.
Finally, DO NOT MAKE EXPLOSIVES, you clearly do understand to much of chemistry or you would not be asking this question(not that that is a bad thing) and you clearly have a ways to go before you can create highly pure nitric acid, because of not only the skill required but also the apparatus. You would only end up with missing fingers if you tried to make explosives now!!!!
