There are a couple of ways to stuff cannelloni tubes:   Spoon Method: This is the simplest method. Fill a spoon with your desired filling and carefully push it into the cannelloni tube. Repeat until the tube is filled, but don't overstuff as it can burst during baking.   Piping Bag Method: Fill a piping bag fitted with a large tip (or even a zip-lock bag with a corner snipped off) with your filling. Pipe the filling into the cannelloni tubes, controlling the amount and ensuring even distribution.