Easing into exercise for people who just DONT

I need help getting into exercising. I don’t know where to begin and how to stick to a regimen. I’m 25 with a 9 month old, I’m not overweight but I’m suuuuper out of shape and my body’s softer than a dinner roll lol I get so out of breath when I just climb a flight of stairs normally so I can’t imagine how running would affect me. It sucks cause when I was a teenager I was so active but the last few years I’ve gotten so lazy. I don’t do ANY exercise, and I can’t remember the last time I ever have. I’m not asking to be super fit with cut abs and all—I just wanna have good stamina and a firm body and walk fast without wanting to collapse.

If anyone can suggest a routine or calendar and any tips I can stick to ease myself back into exercising would be great!