If your project doesn't already have an App_GlobalResources folder then right click the project node and choose Add > Add ASP.NET Folder > App_GlobalResources
Then right click your App_GlobalResources folder and choose Add New Item
Create YourResources.resx (for English we don't specify a culture code because it is the default)
Then in the Feature Settings put YourResources as the resource file name (without the .resx extension)
Then add your resource strings in your resource file.
I do recommend use post build event to copy the .resx file, as well as your dll and .ascx file(s)
The name of your module Setting is what you use for the resource key, it cannot have any spaces in it, but the associated string can have spaces.
Hope that helps,
Joe