Clicking on a marker is demonstrated in Example "Points Of Interest - Selecting Pois". You basically assing a function to the onClick trigger of an AR.GeoObject or any Drawable.
e.g.
var myDrawable = new AR.ImageDrawable(image, 2.5, { onClick: function() { /* do something */ } });
Or open a webpage using AR.context.openInBrowser("<url>"), which opens the supplied URL in a fullscreen browser.
As for the direction: we currently do not offer an API method to get the direction between two points. You can use a 3rd party javascript library that deals with coordinates and allows you to calculate the direction (e.g. http://www.jstott.me.uk/jscoord/).
kunchit surachon