To import multiple images per person, set up an index file that includes both file names on the same row. Below is a very simple index showing two file names, Last Name and First Name. Only the first FileName column must be named as such - you can use any random name for subsequent alternative images.
Import the index as you normally would. When the import is complete, the first set of portraits will appear as the default view.
Click on the Source dropbox to view alternative sets.