How to edit my sims that have been born into the Sim world?

I forgot how, but I know there's a way to edit them as if they are new sims I've created. But I forgot how tho.

I wanna alter a voice of one of my sims. But the problem is she's the 5th daughter of the first generation family. I don't know if born sims can't be changed like a sim that gets added into the game. So please be kind and let me know how I can edit her :smiley:

I'm sorry I haven't shown off the family so far, I'm too lazy to make an account on a picture sharing site and upload pictures of the family so far. But I plan to eventually.