Connexions is both a textbook repository and textbook authoring platform. If you are working with an open textbook from OpenStax College and want to modify the book, you should consider using Connexions as your publishing platform as it is the platform that the OpenStax College projects are built on. If you wish to create a new textbook based on an existing OpenStax College textbook, you should view the create derived copies video.
In this video, you will see how to create an account on Connexions and then upload a textbook created in Word to the platform.
https://www.youtube.com/watch?v=TzeXAVpvg-I&list=UUTfdV8sd55iADYCicIJ8JKA