If you want to install your apk directly on sdcard then you can go for installLocation
(without publishing apk)
or else use Expansion file concept of Android, while publishing your apk you can attach(main|patch) file.
main: Primary resource(application cant run without it)
patch: secondary resource(application can tun without it)
All you need is to collect your content and make a zip, should follow naming format as below
<main|patch>.expansioncode.packagename ".obb" implicitly append why Google.
You have to do Licencing even your app is free.
you must have public key of merchant account.
how to download Expansion Content you can find here
http://developer.android.com/guide/market/expansion-files.html
While downloading you have to pass parameter content size(in byte) to map the file
XAPKFile(boolean isMain, int fileVersion, long fileSize)
http://developer.android.com/guide/market/expansion-files.html#Download