The portfolio system on FX Blue Live can be used by trading groups where each account in the portfolio is controlled by a different person. As a result, there is one account which "owns" a portfolio. If you are logged in as account A when you create a portfolio, then you need to be logged in to account A in future to make any changes to the portfolio.
To set up a portfolio, log in to the FX Blue account which you want to "own" the portfolio. You then go to the Portfolio tab of the first account which you want to add, e.g. https://www.fxblue.com/users/example/portfolio. You choose a name and title for the portfolio, and you can also click on the "Other accounts" link to specify other accounts registered to the same email address which you want to include.