Livestream set up needed

We are a luxury resell platform doing 4+ live streams daily. We currently use a phone and livestream software. We would like to use 2 external cameras and mix between them, and also stream to Instagram, YouTube, Facebook at the same time (our livestream software is compatible to do this already but needs an RTMP - we don't know how to set this up). We need someone tell us the equipment we need, and to set it up for us, then train us how to use it. Thank you!

Based in central London