I have pah and my doctor did a test where I walked for 6 minutes. Should I be trying to walk more often?

Yes. If you mean pad, walking is one of the mainstays of medical management. You should walk a minimum of 3 times per week (more is better) for at least 30 minutes of actual walking time. That means if you walk for 5 minutes and then rest for 5 minutes, that only counts for 5 minutes of walking time. You will notice an improvement over time if you stick with this plan.
PAH. Pulmonary arterial hypertension is quite a unique condition. Your doctor, needs to work out for other condition because this could be multifactorial, or idiopathic (no cause). Regimen is complex and specific for you. Excercise for you will depend on your fucntional capacity based on ny heart classification. I have seen patients live for over 10 years with the newest advances in meds. Good luck.