Just for reference, the following steps were posted about 2 years ago. It may still work!
Step 1
Call your lawyer and get the email address they use to login to the ARI portal - you only need the email address they use (NOT the password) - this email is “registered” with the SEF as the one associated with their law firm - unless it is a single lawyer firm, usually they have a special email they use for their SEF portal login, not their actual email.
Step 2
Create an account for yourself with your email at SEF ARI portal at ari.sef.pt 57. In the sign up flow, there is a place to put in legal representative. Use the email from Step 1 there - the screen will update immediately with the name of the law firm if the email is recognized (before you even submit the form). If that does not happen, you do not have the right email address.
Step 3
You MAY have to do this - I did, but not sure if this is necessary. I entered by US social security number, and my US passport number. DO NOT SUBMIT any documents (as the lawyers usually don’t like that, as they want to control what exactly gets submitted)
Step 4
Now ask your lawyer to login to their portal and see if they can see your account. My lawyer was able to. From here, they were able to submit documentation via their portal, and I am able to continue to see their progress on my account from my login.
Basically we both have access to my account now - they have it through their portal, and I do through mine. And we are both able to edit or submit stuff.