@LindseyBlair ...
I'm not sure I totally understand your question, and so it might be helpful if you provide some more information for the Community. Are you saying that your Gradebook is empty and that you are wanting to know how to add assignments to your Gradebook so that you can start grading student work? If so, you create all your assignments via the "Assignments" page in your course. Any assignment that you set up as graded will then show up as a column in your Gradebook. Here are a couple short video tutorials for you on this:
However, if you are asking about something else entirely, please come back to this topic to provide some additional details for Community members so that we can help answer your question. Thanks!