The plugin and this documentation site assumes you are already familiar with the GraphQL language. If you're not, please visit the official graphql.org website first.
The plugin is hosted in the JetBrains Plugin Repository at https://plugins.jetbrains.com/plugin/8097-js-graphql
You can install it directly from your IDE via the "Settings > Plugins" screen.
On the "Marketplace" tab simply search for "graphql" and select the "JS GraphQL" suggestion:
Compatible IDEs and Versions
The plugin works with all IDEs in the IntelliJ Platform, including but not limited to WebStorm, PhpStorm, IntelliJ IDEA, and Android Studio. The minimum version is 2018.2 (182.711 or later).