You can either tap the double arrows next to your portfolio balance or swipe in from the left edge to bring up the options to switch, rename or delete portfolios. In minimized layout, tap on the 3 dots in the right top corner and select 'Switch Portfolio'.
To switch, simply scroll and tap on the portfolio of your choice.
To rename, tap 'Edit' and then the pencil icon to type in a new name for the portfolio.
To delete, tap 'Edit' and then on the red delete icon to completely remove a portfolio. Please note that this action is irreversible!