This plugin adds a new menu item: File -> Import Shadertoy project. After clicking on it, a popup will open. You just need to enter a link that points to a Shadertoy project and then choose a location on your computer. A new project will be generated and all the required files will be created (note that this plugin also downloads appropriate textures) in the selected location.
That's all! Also, don't forget that some Shadertoy shaders can't be accessed with the API.