Program Viper remote start button?

I purchased a Viper 4115v1 remote start a couple years ago from Best Buy for my 2011 Prius II. It's a basic one-way remote start. Best Buy offered free installation, so I chose that option. It's working fine now, however, I'd like to add an additional remote start button (for the spare keychain). So I purchased a compatible Avital 7111L button from eBay, however, I can't figure out how to program it to work with my existing system. It didn't come with instructions. When I search online, I find instructions for keyed ignitions, not push-to-start.

Can anyone help me out with instructions for programming this second button to my existing system?