How do I use this casio keyboard?

I have a casio wk-1500 yea it's pretty darn old but my dad found it at a yard sale so he just bought it. I want to learn how to use it but since it's not from a store there aren't any users manuals with it and I can't find a single one on the internet. It has a ton of ons and i don't know what any of them do other than the ones change the sound of the keys. I want to use the sequencer on it but i have no idea how. I appreciate any help