All you have to do is take whatever a common trait between all of them are (it looks like .slider), and hide that, like so:
Or, if you want to slide it close, use slideUp() or something (same function you use on the close button).
Do this before you show and you can close them all first. If the one you want to open is acting function, you might want to add something like:
To take "this" (the one you clicked) from the list. (If 'this' isn't the slider, you may have to do something like ".not($(this).children('.slider')" or whatever is appropriate to target it).