This will cover two things: songs and controllers.
First up: songs. Charts in this are basically folders with files. Here's where you can get some:
Then, create a songs folder in the game's directory and move the (unzipped) folders into it.
Next is controllers. If you don't have a guitar, don't worry about this. Set the game to gamepad mode, don't worry about strumming, and make sure to bind your controls. You can probably find a guitar at a Goodwill later.
If you do have a guitar that isn't a Wii guitar, check this spreadsheet for what to do. If you do have a Wii guitar, you're gonna want to buy this adapter. I know this is the free games directory, but the alternative isn't really workable, and this adapter can be used for every Wii controller excpet for the Wiimote.
And that's it! Enjoy the game!