Kung Hei Fat Choy!
This is super easy and can keep children busy for a hours.
Take an A4 piece of paper and let your little one decorate it...they could draw, colour, paint, stick, whatever they like (obviously if they do anything that requires it to dry, then you'll have to let it dry once the paper is decorated.
Then fold the paper in half (long side to long side) and cut from the fold to about an inch away from the edge, do that across the paper, leaving about an inch between each cut.
If you have a 5yr+ child then they will probably be able to do all this themselves, if not they might need help with the folding and cutting
Open up the paper and roll it (so both short sides are together) and stick in place
I've been lazy and used cellotape, but you can use glue
You should have something that looks like this
I like to give it more shape so I push it down gently
Take another piece of paper and cut a strip off the short end
Attach the strip to the inside of your lantern creating a handle
and Voilá you have a Chinese New Year lantern