I want to build a Libra TestNet with two servers.
I don't know how to use config-builder to configure the program.
This answer might be a bit late but it might help for someone who is looking for a solution.
I was able to setup local test network with single/multiple nodes based on the following
libra-swarm
package is well documented here https://developers.libra.org/docs/run-local-network and defines easy steps to setup your local test network with defined number of nodes.