How do I disable auto-correct in Mail V11.5 (3445.9.1) High Sierra?

Oops! Yes, definitely "Thank You!" to you!! I would never have figured out how get that auto-correct to stop if you hadn't given such a clear explanation of what to do. I'm a senior in my 70's who doesn't have thet teen granddaughter/grandson people think we seniors all have. to come over and take care of our computer needs, so I depend on the kind people in the Apple Community like yourself to help me out. You are making a most valuable contribution of your time and energy to reply to user's questions here. I'm very grateful.

Thanks so much! It worked perfectly and I'm delighted!