Brain needs blood. Brain needs enough blood flow as source of cellular fuel. Inadequate blood pressure doesn't supply enough fuel to brain so it doesn't function optimally, eg cognitive impairment. This is very different from lowering high blood pressure towards normal range, which is important in decreasing stroke risk.
Effort matters. You should see positive effects when you can sustain > %80 of your max heart rate for duration > 20 min, in training. Learn about max heart rate, and target heart rate training.
Lifestyle recommendations reduced blood pressure in patients who exercise. What about the rest of us?
Exercise. Everyone shoul try to get some exercise regularly. Some times it is hard to go to the gym or for a full workout, but you can do simple things like taking the stairs or parking away from the store in the lot so you have to walk farther. On these beautiful spring days in is really great to take a walk outside.