Here is a quick way to find, create, assign and add to Portfolios.
They are found under the purple letter in the top left hand side. Only Admin permissions can see users and permissions.
You can create portfolios, add users, add customers, change the portfolio name and delete portfolios on the right hand side.
To add customers to a portfolio, click Customers and choose the customers you'd like in the portfolio. You can either pick and choose or bulk choose. Ensure to click Save.
Use the Filter button within any portfolio to find specific items, such as customers in this example. I can then assign any "unassigned" customers to a Portfolio. Ensure the portfolio and the field are selected in the filter before clicking Apply.
You can see what Portfolio any customer is assigned to from within the customer Confirguration. On the right hand side you can see Managed Portfolios. You can add or remove customers to portfolios from here.
You can then filter quickly within your customer list for any portfolios.