@jennyta Welcome to Canvas! As a new user I would recommend the following items as a necessity:
Set a home page that clearly links where you want students to go.
Start building Modules by instructional unit. Place every resource you want your kids to access within that unit, whether it be PowerPoint presentations, handouts, etc. Having organized modules is key for students who are seeking mastery outside of classtime.
Populate your calendar with events, i.e., class activities that day, and link both module and / or student resource. This is huge for absent students.
Under Settings/Navigation, turn off most everything except the navigation you want your students to access. I personally have everything turned off except "Home," "Modules," and "Announcements." All of the assignments, quizzes, etc I use are found within the modules.