When to call it quits for the day?

Hey all. I am on day 1 of trying to get in shape. I am not overweight at all, but I am incredibly out of shape.

I downloaded c25k and started the first exercise today (5 minute walk, (1 minute jog, 1:30 walk), repeat parenthesis. By the time I got through the first run, I was exhausted. Sweating, panting, lightheaded and wobbly. I decided to go home because I was scared to overexert myself and get too far from home to come back safely if it got worse. I finished the second run on the way back and felt even worse.

I know that is a chicken shit amount of exercise, but im not sure if i tapped out too early or if being lightheaded is a sign I need to stop and try again, then repeat until I can handle it. It got slightly better during the walk breaks, but not to the point that I was no longer light headed

Again, this very well may be a stupid question. I dont know what exercise is supposed to feel like.