add illustration for the N preview procedures

Change-Id: If775af9b9a46ce2ef31f938ee3b6b452cdc49482
diff --git a/docs/html/preview/setup-sdk.jd b/docs/html/preview/setup-sdk.jd
index ac09c3a..36a14a0 100644
--- a/docs/html/preview/setup-sdk.jd
+++ b/docs/html/preview/setup-sdk.jd
@@ -28,6 +28,9 @@
 href="{@docRoot}preview/download.html">Test on an Android N Device</a>.</p>
 
 
+<img src="{@docRoot}preview/images/n-preview-setup.png" width="700" alt="" />
+
+
 <h2 id="get-as13">Get Android Studio 2.1 (preview)</h2>
 
 <p>Developing for the Android N platform requires Java 8 and a new