How do you lose weight with hypothyroidism?

I have recently been diagnosed with hypothyroidism, and while losing weight shouldn’t be a priority, I have gained over 50lbs within the last year and a half. It is destroying my self esteem, and making me depressed which isn’t helping my physical symptoms. I get 12k+ steps a day at work, but exercise makes me feel dizzy and weak. I have already struggled with losing fat in the past, and it seems no matter what my diet is I just keep packing weight on. I am 22f. Please help.