Portfolios are a group of stocks. A Portfolio can contain many stocks. A stock can be part of many Portfolios. Some people use Portfolio to regroup by brokerage accounts, some people use them to regroup by commodities, by market, there are no rules.
To change the name of a portfolio, press the Edit button at the right of the portfolio name.
To add or remove one or several stocks from a portfolio, select them and simply drag them to the content list, reverse the operation to remove.
To add a portfolio, select the last row, with a + button, and press the green +. To add a subfolder to an existing portfolio, select the portfolio and press the green + button.