Steps to follow to upload picture on Wikimedia Commons
First, you need to have a Wikimedia account. The same account is good for all Wikimedia projects, including Wikipedia and Wikimedia Commons. It is totally free.
Make sure to include the Wikidata-Item ID (search for the protected area and copy the Q-number at the top of the page) corresponding to the protected area on your pictures if you want your picture to be eligible for the contest or use the upload link provided in the lists. Include it by using the template with the following code: |description={{Protected areas in Canada|Q1234567}}.
For those who do not know how to locate the Q-number using the above Upload instructions, go to the Wikidata site and search for the park or other protected area in Wikidata. Wikidata will bring up the page for that park or protected area and it will have the Q-number listed there.
