Welcome aboard
d0nbr0wn1ng 
I try to avoid Steam and UBIsoft "uplay" (now "Ubisoft connect") like the plague, but now since you bought it it should at least work – if the game is installed on your HD you should be able to find it, *.exe and all.
I always bought the DVDs so i do not know how to help - with "Steam" a game is usually installed in the "Steam" directory, the same will be true for this Ubisoft connect procedure.
Problem is that official updates are usually automatically filled in when you buy a game, but there will almost always be problems with inofficial mods.
Greetings, Catfish