To profile your Silverlight applications use Profile Silverlight executable... action on Welcome screen or in "Profile" menu.
The window will appear:
Choose profiling options, then press Profile to launch a profiling-enabled browser instance.
Important: some browsers do not allow running more than one instance at a time.
Although you can open several browser windows,
they all may belong to a single underlying browser process.
To ensure that a new browser instance will be started, it is strongly recommended that you close all browser windows before you press Profile.
The profiler will automatically connect to the application as soon as it opens in the browser.