Things You'll Need
Instructions
Get the lenses. Finding lenses good enough to make a decent telescope and sturdy enough to put in a child's toy is difficult. One method is to buy cheap toy magnifying glasses and use the lenses from them.
Put one lens in each end of the cardboard tube.
Look through the tube. If the image is blurry, adjust the distance between the two lenses until the image becomes reasonably clear.
Cut or peel off the excess of the cardboard tube.
Glue the lenses in place.