At first, this solves fairly simply.
Each picture clues a word. The word has the same number of letters as the number of numbers next to the picture. Put each letter in its corresponding blank. (For example, the top left picture is a SNEER, so S goes in square 32, N goes in 22...)
The pictures are:
SNEER / ZIM / DIME / GURU / ART / ACE / (Kylo) REN / NAVAL (the typo, should be "navel") / COCOA / STAIR
And the message is:
MAD MAGAZINE, REAR COVER: INSTRUCTIONS ARE A CLUE
So, what do we do next?
Mad Magazine is well-known for its "Fold-Ins" on the back cover, humorous cartoons that fill a page. When folded, they give a completely different image altogether. For example:
The trick to this puzzle is that...
it's also a fold-in!
The message at the bottom now says "this is the answer", and all the numbers in the grid below correspond with the new images. Repeat the same process (the images are DOWN / HOME / LEFT) to get the final answer:
You have to know WHEN TO FOLD 'EM.