Connect a second on-premises site to a virtual network

I've setup a site-to-site VPN from my loccal network to Azure virtual network, all in Resource Manager Deployment. The VPN gateway created in Azure is already route-based. Now I need to connect a second local network, that is in a different branch office, to the same Azure virtual network.

I know this involves using Powershell, but I can't find the specific steps to follow. Basically, I need the analogous article of this:

https://azure.microsoft.com/en-us/documentation/articles/vpn-gateway-multi-site/

but for the Resource Manager Deployment.

I'm stuck without it.

Thanks for helping