Running is a great exercise. Humans have run since our beginnings, and it is a great way to get fit, lose weight, and complement other forms of exercise. However it is not low impact and one needs to start slowly.

First of all make sure you have your doctors OK. Assuming there is no medical reason not to run, you can get started. Depending on your level of fitness, you may need to get started very slowly. Even if you are relatively fit you will stress your muscles in new ways so you will still need to start relatively slowly and build up.
You can start by alternating walking and running. This is an excellent beginning, and I even know seasoned marathoners who alternate between the two. You might start with a goal of between one quarter to one mile, and alternate every few minutes.

Make sure you have a decent pair of shoes. You don't need to spend hundreds of dollars to get started, but something comfortable and flexible. I started with the sneakers I already owned and only bought special sunning shoes after I became semi-serious, and those were not expensive either.

Increase your mileage slowly! Perhaps only 10 to 20 percent per week. Also, never run multiple days in a row. I might run two max in a row, with at least a day off to let the body recover. Initially you'll want at lest one day off between runs.

Vary your pace. Different speeds are great for you. So is different terrain. Uphill, downhill, flat, through the woods or across grass carefully, and so forth.

Running is a great exercise that almost anyone can do. Many do it well into their 80s and beyond, and with todays frantic schedules, it's a great way to concentrate a lot of exercise quickly as running is time efficient.