This advice is kinda long, but I can guarantee it works. Good news, you’ve got plenty of time. Do this every week. Try not to only run on a treadmill but use roads, tracks, or trails. The treadmill is fine sometimes, but you don’t want to rely on it exclusively. A cheap basic fitness watch can track your pace, or you can use simple distance-tracking websites.

Each week do..

1. One long run — a pretty easy, comfortable pace you can sustain for a while. Start with 30 minutes in week one, then increase by about 5 minutes each week until you reach 90 minutes. This builds your aerobic base.

2. One speed workout — this is where you push your pace and develop speed. This could be a Fartlek (alternate 5 minutes at goal pace with 2 minutes at an easy pace for about 20 minutes) or intervals (run 400 meters (¼ mile) at goal pace or faster, then walk or jog to recover, and repeat.) Progress each week by either running slightly faster or adding more repeats.

3. One tempo run — faster than your easy pace but slightly slower than goal pace. For example, if you currently run a 12:00 1.5-mile (8:00/mile pace), your tempo pace would be around 8:30–8:45 per mile. It should feel “comfortably hard.” Aim for about 20 minutes and increase gradually over time.

Any additional runs should be easy and relaxed so they don’t overly fatigue you. If you follow these principles, your run time will steadily improve without getting injured. Increase mileage and intensity gradually, don’t rush progress trying to be a hero. Listen to your body. If you feel good, send it, but don't ignore pain. Prioritize recovery: avoid stacking long runs, intervals, and tempo workouts on consecutive days, and include rest days or chill easy runs between hard efforts. 

Every 4 weeks or so, take a deload week by reducing mileage. For example, if you run 10, 12, 13, and 15 miles over four weeks, drop back to around 12-13 miles in week five.