The following instructions work for other JetBrains environments. Here I only added the Solidity plugin to WebStorm and PyCharm.
The latest version of the Solidity plugin is available here: https://plugins.jetbrains.com/plugin/9475-intellij-solidity
Download plugin - Zip file
- Do not uncompress
- Copy to it's own directory
- WebStorm/PyCharm -> Properties
- Plugins
- Install Plugin from Disk
- Restart WebStorm/PyCharm