How to extract the keyword from a mono-alphabetic substitution cipher

Question

I am a beginner to cryptography and i have the following the question. I know that to extract a plaintext from a mono-alphabetic substitution cipher i can perform shifting the characters by n times until i have the plaintext, or i can also use the frequency letter analysis. However by doing this im getting only the plaintext and not they keyword thats been used. The answer might include creating a table with the alphabet linked to the corresponding letters used in ciphertext by following the frequency letter analysis but im not sure how this works. Can someone explain to me how i will be able to get the keyword?