When the new semester rolls around, you have a couple of choices. You can start over (which you probably don't want to do and since that doesn't involve any more steps, you can stop reading now) or you can copy information from a previous course, which is what I'm going to assume you want to do.
In Canvas, click on "Courses" from the left side menu, then click on "All Courses" near the bottom of the slide out menu.
Before you click on the course that you are going to work on, you might want to click the star to the left of the name, so that it appears on your Dashboard and in your short list of courses.
Now that you have the courses selected, click on "Settings" and then choose "Import Content into this Course" from the right side of the screen. Note: if you are using a narrow screen, these options can be "bumped" to the bottom of the page. If you don't see them on the right, just scroll down.
When you get to this screen, you will first choose the Content Type. You want the first choice: Copy A Canvas Course. As you make choices, other options will appear. Working our way down this screen, you will come to the following options:
When you have the setting entered, click on the blue Import button at the bottom of the page.
If you chose to select the content that you will be importing, you'll do that now. Click on the blue Select Content button for the class that you are working on.
You'll have to look through your content and decide what you want to carry over to your new course. If there are things that you know you will not be doing, then don't select those things. The only thing I didn't carry over were Announcements. If you are importing from the first semester of a year long course to the second semester, you might want to be very selective in what you import. You probably always want to copy Course Settings and Syllabus Body, after that it's up to you. I would say it would be better to import too much than too little. You can always delete things.
You can sit around and watch the little "running" animation if you like. Eventually it will change to "Completed". Now go to your course (it's on your dashboard if you remembered to click the star in step 1), and change it from Unpublished to Published.
You should probably check on the due dates of at least the first week or two of assignments just to make sure they shifted in a reasonable fashion.