Synap separates the idea of 'courses' and 'assignments'.
A Course is composed of tests, quizzes, videos and other content on a particular topic. It is the content that you want people to learn.
Once you have made a Course, you then create an Assignment in order to send it to a particular group of users.
The reason for splitting them up like this is that it makes it easier to separate the core content of your courses, and the specific rules, deadlines and processes around assigning it to different people. It also means that you can assign a course as it is at the time, without impacting historical data or in-progress attempts if you update your course at a later date.
Courses are the 'what'
Assignments are the 'how and when'
User groups are the 'who'
In a nutshell: First, create a course by adding in content from your library. Then, assign it to the appropriate people in your organisation.