How do you decode the ADFGVX cipher?

To decode the ADFGVX cipher, first, you need the polybius square used for encoding, which consists of a 6x6 grid containing the letters ADFGVX along with the digits 0-9. Once you have the ciphertext, replace each pair of letters with the corresponding character from the grid. Then, rearrange the resulting plaintext based on the transposition key used during the encoding process. Finally, read the plaintext to reveal the original message.