Installation via OpenUPM

Unity Package Manager, or UPM for short, is Unity's new solution for managing packages so they don't need to be included inside the /Assets folder.

Have a look at the Unity Package Manager docs for more info.

OpenUPM is wonderful initiative by @favoyang that takes this one step further by providing a unified registry and command-line tool for distributing various packages supporting UPM deployment.

Prerequisites

1. Requires Unity Editor 2018.1 or above, as UPM was first shipped with 2018.1.

2. OpenUPM-CLI

Installing the package (Cloudsmith registry)

Run the following on the command line:

openupm --registry https://npm.cloudsmith.io/jillejr/newtonsoft-json-for-unity/ add jillejr.newtonsoft.json-for-unity

This installs the latest package from https://cloudsmith.io/~jillejr/repos/newtonsoft-json-for-unity/packages/?q=name%3A%27%5Ejillejr.newtonsoft.json-for-unity%24%27

Installing the package (OpenUPM registry)

Run the following on the command line:

openupm add jillejr.newtonsoft.json-for-unity

This installs the latest package from https://openupm.com/packages/jillejr.newtonsoft.json-for-unity/

Updating the package

Updating the UPM package, even if installed via OpenUPM, is identical to the instructions found in the wiki page Installation via UPM - Updating the package.