How does plugin:CreatePluginAction() work?

Hi devs, I’m trying to use input in a plugin I’m making, but I can’t seem to figure out how.
I’ve read the docs on PluginAction, but I can’t find any way to set it up. When I use plugin:CreatePluginAction() I get an error (“Argument 3 missing or nil”)
I’m also not sure how to bind keys, can anyone help with this?