In Book Creator online, a teacher can create a library and invite students to join. Note, this feature is not available in Book Creator for iPad.
Each teacher starts off with 1 library that can accommodate 40 books (more libraries and books are available if you upgrade to a paid subscription).
Creating another library
Click on the Teacher Dashboard icon in the top toolbar (the 3 lines in the far left of the toolbar). This will bring up the Teacher Dashboard, like below.
Click the + Create a new library button.
Give your new library a name, and adjust the library settings for student permissions.
Click the create library button.
Next, you'll want to know how to Invite others to join your library.
Edit the name of a library
Open the library and click on the Settings icon in the top right to edit the libraries name and settings.