I think that should be obvious from the instructions. And HAL’s cryptogram helper only works with monoalphabetic substitutions ciphers, with the restriction that no letter can substitute for itself. I have an octave/matlab script that converts plaintext to MASC, with that precise restriction, if you think you would like it.
These cryptograms are meant for amusement, and provide a convenient gathering place. They are not intended as any deep intellectual challenge.
When my daughter was in high school, she and I would solve crypto quotes for extra credit.
Frequency analysis.
But it has been a long long time since I did that.
Thanks.