Zoom comes pre-installed in Canvas and you can use it to create time slots for students to sign up for appointments with you.

How to set up appointment slots:

Click on the Zoom link in your Course's navigation menu.
Click on the Appointments tab at the top of the page.
Click the + Create Schedule button.
Select the day(s) you would like to have office hours.
For each day, choose a start and end time for each day. You can also click the circle with a plus in it to add a second time slot to the same day. You can do this as many times as you need.
Optionally, check the box next to End repeat on select the date after which you no longer want to use this schedule.
Set how long you would like each appointment to be for.
Add a name and (optionally) a description for your office hours - perhaps a list of topics students might want to meet with you about.
Optionally, check the box next to Apply schedule to all courses.
Click Create. You should be able to see a slot with the name you chose beneath the +Create Schedule button.

Tip: to increase visibility, move the Zoom link up in your course navigation menu by going to Settings > Navigation and dragging the Zoom link up the list and then saving it. You may also want to create a page in your starting module with instructions for students.

How students can sign up for appointments:

Click on the Zoom link in the course navigation menu.
Click on the Appointments tab at the top of the page.
Navigate through the available slots by clicking on the arrows at either end of the list of week days.
Click on the time you'd like to meet on the day that works for you.
Click Book.