Bubblemod is a standalone game which uses Xash3D FWGS engine.
To play it, make sure you followed these steps:
1) Installed Xash3D FWGS and Bubblemod
2) Copied "valve" folder from your Steam account to your Android device. (e.g. to "xash" folder on your device storage. If you choosed another folder, make sure you are choosed this in Xash3D FWGS app)
Full information on bubblemod.org