Oh ok
You have to sit your pup and gently pick her paws up so as her body so the pup sits straight. Keep holding the pup and Say word "beg" and with another hand hold the treat above pup's nose after that give a treat. Keep on repeating until she gets the idea to sit straight like that. The treat above pup's nose would help a lot. Just make sure she wont fall backwards.
My Maxi is so wiggly I had to teach him beg trick on the couch first. The couch back helped a lot for the balance to sit straight.
Whew hopefully I was able to explain the trick