The Norvel Twonk Chocolate Frog Card can be found in "Harig's First Lesson".
|“||Norvel Twonk famously died saving a Muggle child from a runaway Manticore- an act which earned him a posthumous Order of Merlin, First Class.||”|
LocationOne can find this card in Moment 3 of the sixth chapter. It is on the second zoom level, on the ground in front of a grey schoolbag.
There is currently no use for this card on Pottermore.