First, you'll need to enable the Attendance tool on your navigation bar in Canvas. To do this, you'll go to the Settings tab and click on Navigation at the top of the page. Then, you'll need to drag the Attendance tool from the disabled menu to the top, active menu: 

Once you've clicked Save at the bottom of the page to confirm your changes, you'll see Attendance now available on the navigation bar. When you click on the Attendance tool for the first time, you'll see a list of students within your course. Click on the Edit Seating Chart button at the top right of the tool to begin creating your seating chart: 

You'll need to drag and drop students from your class list into the available spaces within the Attendance tool. It should look something like this when you're done:

At any point, you can rearrange students or remove them from your active seating chart by dragging them back to the class list. To actually begin taking attendance, you'll need to click on the Take Attendance button to the left of the Edit Seating Chart option. To take attendance, you'll simply click directly on your students. A green check mark means the student was present in class that day, whereas a red x will mean that student was absent: 

You'll see the class date is also available at the top right of the page. Every day, the seating chart will refresh and you'll be able to take attendance again for that specific day:

Note: Taking Attendance in Canvas will create an Assignment titled Roll Call Attendance worth 100 points. This is a default setting. To change the point value or make attendance ungraded, all you'll need to do is Edit the assignment and chose "Not Graded" from the "Display Grade as" category: