>>76301128
>400 lb
Best thing for you is probably just walking. Anything more intense might cause you to hurt yourself. You got a way to track your heartrate? Just go for a walk and see what heartrate that puts you at.

Megafats like you need to be careful about trying to do too much too quickly if you've been sedentary for years. Ease yourself into being more active, start with low impact stuff like walking, swimming, then build up to more advanced stuff like lifting, jogging, biking ect.

You can start with basic body weight stuff, sit down on a bench then stand back up, do this 3x10 times or until you're tried / short of breath.