Answer:
For the present conjugation of poder, you change the o to ue (puedo). For the present conjugation of poner, it is just pongo, pone, pones, etc.
In the past tense, poder becomes pude, pudiste, pudo, etc., while poner becomes puse, pusiste, puso, etc.
So possibly, the difference would be that poder has the change from the o to the ue in the present, but in the past tense they are the same except for the difference in the "d" and the "s"
