Like others have said - couch to 5K or similar, definitely follow a plan. Following a plan can help prevent injury from overuse or burnout if you’re not making progress. I would also suggest active stretches as you get ready to run. Swinging your legs, high stepping, butt kickers, side lunges, walking lunges, etc. The idea is not to increase flexibility with these, but rather to warm up- and don’t do anything that hurts! There’s no need to go nuts. Just to get muscles moving a bit before running