Hi, I'm a little confused and hope you can help out.
Each site will use the same theme and plugins. Only the content will vary.
Hence we thought your multi domains plugin would be ideal for us. We have set up a master site and installed Wordpress multisites following these instructions found here https://premium.wpmudev.org/blog/how-to-build-a-wordpress-multisite-network-with-multiple-domains/
We have also installed Domain Mapping and Multidomain plugins. But the next steps are unclear and we have not been able to edit any sites we have added.