Forum:How do i add js

i see js some place and i want to add it but i dont know how

here is js i want to add

$.getJSON('/index.php?action=ajax&rs=ChatAjax&method=getListOfBlockedPrivate', function(response) {	$('head').append('li[data-user="'+response.blockedChatUsers.join('"], li[data-user="')+'"] {display:none;} #Rail li[data-user] {display:list-item !important;} '); }) NodeChatController.prototype.blockAllowPrivateAjax = function (name, dir, callback) { $.ajax({		type: 'POST',		url: wgScript + '?action=ajax&rs=ChatAjax&method=blockOrBanChat',		data: {			userToBan : name,			dir: dir		},		success: function(data, textStatus, jqXHR) {			 if(typeof callback == 'function') {callback(data, textStatus, jqXHR);}			$.getJSON('/index.php?action=ajax&rs=ChatAjax&method=getListOfBlockedPrivate', function(response) { $('#ignoredUsers').html('li[data-user="'+response.blockedChatUsers.join('"], li[data-user="')+'"] {display:none;} #Rail li[data-user] {display:list-item !important;}'); })		}	}); }

i ask in chat but nobody choose to help me :(
 * Dealt with this on Chat. 23:12, August 31, 2013 (UTC)