Design the menu link and an ‘active’ state of it as well (I’d add a nested class of active). Then I would create a div to hold the sliding menu and style it properly. Then simple creation of interaction could do the trick. Also as @thewonglv said you could try with dropdown menu as it will work great without having to style active state as well as no code would be required.
Go for dropdown and tell us the results, or hire someone to do that for you if you’ll encounter any troubles doing so. Maybe someone on forum will help you as well? :)