The simplest way of playing is to create a face-down map deck by counting out a number of map cards depending on your level. The stairs card is also added into this map deck.

As always, the whole shuffled item deck is used (without the unique cards), while the treasure deck is made from just the cards that are of the players level or lower.

Starting on the entrance card, explore the dungeon until either you choose to leave, die, or draw and play the stairs card.
Once the stairs card is placed, the player may descend the stairs.  
At this point, shuffle all the played map cards together, including the entrance card but not including the stairs card.  Start exploring with the stairs acting as the entrance card, but add 1 to every roll on the encounter table.  Should the player draw and play the entrance card, they can return to their Town but increase their level by one, improving their character accordingly.  Once a character is a higher level, they will have access to better treasure and items, but face stronger monsters.