It would depend on the dungeon. In any case, the main way to get experience is to finish a quest or sub-quest, which usually means talking to an NPC at the end of it. Just defeating enemies--even a full dungeon of them--- doesn't give a lot of experience.
Your question is difficult to understand because you have not provided enough context.
My guess is that you ported to another higher wizard in Celestia and were hoping to gain a lot of experience by doing the Portico or Solarium.
The dungeons in Celestia give you experience proportional to the level you are at at the time you do the dungeon. Since you are at level 5 you are given experience at the end equal to the amount required for you to raise one level.