Q: How reset password on airport express

My airport express light is flashing aber and I think I need to change the password I don't know the password I used when I fist set it up. All I had was a net book I now have iPad and a laptop but I use my pad more.

I had  the airport express sitting behide a book shelv and have just moved it to fine it flashing it still works but I want stop it from flashing what do I do.