Okay, so this isn't really a story so much as a letter that sets up the framing device of the rest of the stories.
Not sure what a framing device is? Just head on over to the "Writing Style" part of this learning guide, and we'll just hole up here and wait for you to come back. No, seriously, go ahead.
Ready? So, basically, in this letter, Tevye congratulates his buddy Sholem Aleichem on all the fame, and then does a little modesty dance about how excited he is to be in one of Sholem Aleichem's books.
And then of course he hints that maybe some money sent his way might be nice also.