How do i get to Narnia without using a wardrobe?

There are several ways, and they all seem to have a limited number of times they can be used.

1. Through the Wardrobe. In The Lion, the Witch, and the Wardrobe after the children came back into their own world, the professor said to Lucy that she wouldn't be able to go back to Narnia that way.

2. Through blowing Susan's horn (Prince Caspian)

3. The Magician's rings (The Magician's Nephew)

4. Being pulled back in through no action of their own - as they were pulled through the picture in the Voyage of the Dawn Treader. In The Silver Chair, Eustace describes it as magic.

5. Through a magic door (The Silver Chair)

6. Through death (The Last Battle).