So, I think you are supposed to trust a BP taken at home when it is done first thing in the morning? Losing weight helps BP. Regular exercise is a must. They report that even 30 minutes a day of brisk walking will help BP and it can be broken up into segments as long as a segment is at least 10 min at a time for an effect.
Dash diet. There are lots of books on this. Sodium is part of it and that was hard for me. But you have to look for low sodium options. This means all canned goods and prepared foods have to be scrutinized. Tomato based canned products, even canned green beans! They make low sodium versions and this is what you need to go to.
Eating kind of clean is a start. Less prepared things in general, no fast food, etc. I make things like chicken rice soup made with brown rice. Fish that is baked with lime juice. Fresh vegetables, steamed. Salads. Low sugar peanut butter with celery. Hummus with carrots.