Here is the video to add canonical tags in DNN dynamically
Step 1: Hover your mouse on Admin and select Site Settings.
Step2: Click on Site Settings
Step3: Click on Advanced settings.
Step4: Click on Site aliases section in the accordion provided.
Step 5: Click on Add New Alias button.
Step6: Paste your URL in the text box provided and check the checkbox beside and save the link.
You are all done. Canonical tags will be added to all the pages accordingly.