You can create a collection pretty much any way you want. All that matters is how you get it into BibServer.
We presently support upload from URL or from PC of bibtex, csv, and json files. These are converted into BibJSON where necessary, and stored in the BibServer index.
Once uploaded, you can access your collection at the provided URL. You can refresh your BibServer collection by simply reloading from wherever your collection file already exists.
It will eventually be possible to browse records in BibServer and create a new collection out of them, but this functionality is not available yet.