In this post I will try to consolidate the resources I have used on this site. I always have trouble finding a post that details steps I need at a future time. Link to the portal https://www.portaldasfinancas.gov.pt/at/html/index.html
1. Obtain access to the Portal is your first step. We had a fiscal rep and they provided our password after we registered on the site. Some fiscal reps will register you and then give you the password.
How to request access? This was provided to us by our FR. It was necessary and we missed this step for 6 months until Gilda from Ei! mentioned it in May 2021 on an EP YT video.
"If necessary, you can request the password to access the Finance Portal.
www.portaldasfinancas.gov.pt at REGISTER by entering your taxpayer number (TIN), email (optional), telephone (optional), tax address (it is in your TIN document on the first page in the REPRESENTANTE field), choosing a question and an answer. The average time for receipt of the password is 5 working days. As soon as we receive it, we will send it scanned in your email.
All matters and changes related to your TIN must be requested directly on the Finance Portal through E-Balcão."
How to change your password: https://support.bordr.io/article/290-how-to-change-your-password-on-portal-das-financas
Now that we have access and know how to update our passwords, I will keep posting the resources I have found and used on this post. Here are a few members off the top of my head that have helped me: @blaze451, @Antonio_F, @old-bloke, @x-camone, @sonia