I want to change the web address that portfolio has given me by default for my portfolio website

If you're asking how to change your default URL from https: // username . myportfolio . com / to a custom domain name, please read the following help article.

I-already-have-a-custom-domain-and-I-want-to-use-it-with-Adobe-Portfolio-What-should-I-do-

Sorry.  I don't understand what you're asking.  Maybe you can re-phrase it better?

Portfolio Knowledge Base  and FAQ -- https://help.myportfolio.com/

For Portfolio support, please submit a help ticket at the link below.

https://help.myportfolio.com/hc/en-us/requests/new?ticket_form_id=177168