This is another one of those “do it once and forget it” things. I always have to look it up because I do it so rarely. Do it once and then just look it up again the next time I have to do it.
While in your project, run the following command in the Package Manager Console:
PM> Install-Package Newtonsoft.Json
Open the package manager console:
Enter the command in the package manager console
Enjoy working with JSON!