You could turn them into a song or even make it memorable and fun by playing a game that'll help you to memorize them such as playing cards or things like that. I hope that helps! :)
The way I memorized mine was constant practice. And over time, you just have them memorized. Do worksheets, and time yourself to see how fast you can do the problems. Keep doing this until you don't even have to do the math to know the answers.
