To get to the portal on the petitions website, if you're logged in as a member of Parliament, there's a button that appears at the top that says in green either “Member of Parliament” or “Député”, en français. Clicking on that button will bring you to the MP portal from the petitions website.
Also, whenever there's something that appears in your portal, you'll also get an email alert and you can click on a link that will bring you there.