When it comes to things like triplets editors are lazy and don't bother to put all of it in. I dealy you put a bracket round the notes and place a 3 (or in some cases other numberslik 6,7,9 or whatever)
What it meens that the notes which are triplets have a different lengeth.
You can fit three quwaver triplets in the same time as two normal quwavers.
If you look at the time signatur it's 4/4 (for the fantazia) so if all the notes where just normal quavers there would be to many to fit in that bar but they can because there triplets.
Sos it's a bit late and I'm not explaining very well but I hope you understand. I'm afraid that I don't know of any sites for music theory but you can get hold of that stuff for pritty cheap in any music shop.
So any way, No the 3 has nothing to do with fingering in this case and is onlly relevent to the groups of three notes for the first 9 bars which just meen each three have taken the place of where there would normally be two. Anyway have fun