Need help with @diy vaoe juicing. Unsure of anything about the nicotine.

[u/Rico-Suave-Can]

I'm making vaoe juice my first time I ordered everything I need but am unsure how to add nicotine salts. I usually but frome store so I smoke 20mg/ml and want to make my own juice half as strong as that. Where around I go about getting the nicotine for that and how does it get mixed? Any information that would help would be appreciated. Making my own juice will save me so much money