Items in one class interacting with characters from another?

Hey guys, I've got a bit of an issue, thought I'd check and see if anyone could help me out with it.  Seems easy from the outset, but I'm just stumbling over a little part at the beginning.

So myself and my partners (group of 3) are in an intro C# class, and we can't seem to get ourselves into this one part.

Our game is completely text-based - Essentially, we have a game setup where we have a group of characters that are racing around a track, and the players have the ability to use items ON those characters.  Now, turn by turn these items are randomly generated, so we've got that down so far.  Basically, I want to know what we have to write to have the items actually interact with the characters.  We have items that we want to have different effects on different characters (for example, we want Dim Sum to give Character 3 a movement bonus of 2, while giving Character 3 a movement penalty of 2, etc). 

Anyone have an idea as to where I would get started on this?  We've setup separate classes for items, characters, etc...  just need to know how to make them interact.

Thanks guys!