A portfolio is a way to group your share holdings together and track their aggregate performance.
You may set up a portfolio for your SIPP and another for a child's ISA.
To create a new portfolio, log in and go to the Generator
Select the orange button "Add Portfolio" and follow the steps to add a new portfolio.
You may choose to create a portfolio with an opening balance. This is useful for tracking the performance of an initial cash amount.
If in doubt leave the opening balance blank since you can always set it (or remove it) later. Here are instructions for how to set or change your opening balance.