Are you retarded if you don’t know how to use a washing machine?
I don’t know how to use it.
No one is retarded for not knowing things.
Knowing you don't know, and ask for directions is good.
Hiding that you don't know it is silly.
So, you are already half way. Acknowledging this is a skill you don't know yet.
And if it is comforting for you. I explained a new washing machine to someone way over 40 this year. He got lost in the options of the new one. So, I wrote him down the two options he might need for washing.
Ask your parents to write down step by step what things to do for a white and a coloured washing, and you are ready to do it on your own.