The AssetBundle itself is just the assets loaded into memory, it cannot be saved to the disk.
On the other hand, the WWW object, downloads the file itself, so before converting the WWW result into an AssetBundle, you can save it to the disk, using WWW.bytes to get the bytes, and File.WriteAllBytes() to save to disk.
by any change , would you know how to implement the [file browse dialogue code][1] I have never come across a code structure like this. [1]: http://wiki.unity3d.com/index.php/ImprovedFileBrowser
– Alanimatorthanks for the help . I see how its done now .
– Alanimator