You learned this reading with the kanji, but here's an extra mnemonic just in case:
How do you read flatulence? Heh(へ)...heh..heh..heheheh. You can't NOT laugh at the word flatulence.
As with the kanji, some dictionaries incorrectly list おなら as a reading for this word, because the meaning is the same.
I'm assuming you are talking about flatulence, am I correct?
If I eat pork, I fart a lot.
Those farts were pretty satisfying.