If one has CHF is exercise to be encouraged, even if it makes them tired quickly and get short of breath? What is optimal amount of exercise for chf?

Routine. talk to you doctor about your specific situation, but in general exercise is good. do what you can, then stop and rest, then go again. if you get lightheaded or chest pain - review with your doc. i'd strive for 30-60 minutes most days of the week of routine dedicated exercise.
Rest. Better to rest , but more importantly, have follow up to be sure meds are appropriately helping maximally - especially if legs are swollen, or difficult breathing, or swollen neck veins when lying back slighltly. Routine excercise is encouraged but only up to capacity - which would be any of the signs above or just plain fatigue.