Well I don’t know how you’ve been eating, but it’s not always a great idea to try and instill too many disciplines at once. That’s a great way for someone to fall off the wagon in a few weeks.
First thing I’d do is just start eliminating things like caloric dense/ low nutrient value foods. Don’t worry about counting calories or macros right now outside of protein. Just focus on eliminating “bad stuff”, like pops/coke, candy, desserts, fast food, etc. Stick to whole, mostly unprocessed foods and learn how to just eat normally again. I say normal, but I think you know what I mean.
Training wise, one thing I like to have people do in this state is to just walk for a few weeks to build some conditioning base. This makes gym work so much easier later on because you’re not so gassed after a few hard sets. Plus, just the walking at first is easy to recover from, feels good, and is easy on the joints. Get 30-40 minutes in three to four times a week for two or three weeks, then put in some gym time 2 or 3 times a week after that.