Storing global var in WebStorage?

What is the easiest way to store a global variable into WebStorage and then input WebStorage data back into the variable?

I want the checkbox in sound off/on to be preserved when exiting the game. Is there a better way to do this?

there is a lot of info in the manual entry https://www.scirra.com/manual/120/webstorage

And there is also a tutorial explaining the topic:

https://www.scirra.com/tutorials/266/webstorage-how-to-save-ingame-information