Installing TextSecure, but missing Google Play I am running a custom ROM (Android 4.2.1) and want to install TextSecure from Whisper Systems. To support push messages Google Play is needed for Google Cloud Messages.

How can I install Google Play? 

EDIT, installing the google package fails, installation aborted every time.
Install the Google package for your custom ROM. For instance cyanogenmod you flash the ROM then the Google package, ask whoever made the ROM for the correct version you need, most developers would put instructons in the first topic in their thread.