Installing Bulk Texter Lite
The best way to install Bulk Texter Lite is via one of the officially supported web stores:
How to use Bulk Texter Lite
After installing Bulk Texter Lite, you can open it by clicking the puzzle piece / extension menu at the top right of your browser, and then clicking the Bulk Texter Lite icon. You can only use Bulk Texter Lite while you are on the Google Voice page you are wanting to send texts on.
Bulk Texter Lite will walk you through the account setup process. Follow the instructions to get started.