I am completely lost and don’t know where to start. 100 lbs overweight

I am 100 lbs overweight. I am 5’3 and 250 lbs. I’m extremely tired all the time. I’m 23 and my 93 year old grandma can outrun me. Can someone help me break this down. Doing all the research is overwhelming me. What is step 1? Step2 etc....