Portals default to a 'mini table' like layout when you first create them, but you can then modify them to resemble "mini-forms" instead.
Click the portal (not a field in the portal row) to select it while in layout mode.
Grab a selection handle and drag dow to resize the portal row to be taller than just one row of fields. You will also likely need to open portal setup and reduce the number of rows visible at one time in the portal so that your resized portal doesn't extend off the layout.
Now you can reposition fields as needed within this larger portal row. (And you can use the field tool to add more fields to the portal if that is needed.)