Pulling data from a class instance that may not yet exist in Java

In my Data Structures with Java University Course, we've been tasked with making a simple Social Network.

One of the profile methods defined by a given interface is recommend, which is supposed to go into the array of profile objects holding the list of people. This instance follows, pick one, go into that instance's array follow list and return a profile from there as a suggestion of someone to follow.

I don't really understand anything about how to go about this, because I'm supposed to anticipate an instance of a class which doesn't exist yet.

I don't expect whoever responds to do my homework for me, but any guidance about how to start this would be greatly appreciated.