Couch to 5k maybe.
Generally younger runners do a great deal of interval work compared to most of us olduns.
It's very easy to include intervals in your runs just by running fast then jogging, then running fast etc. You can use lamp posts or similar to mark your distance. I used to run laps of a pond, one fast, one slow etc.
Building endurance can be done in a similar way - jog walk or jog run. Generally if you want to run further you need to run slower. Building up the distance slowly. You need to be running 3 or 4 times a week. other exercises maybe useful as well.
Our young runners do a greatdeal of drills and the older runners do a lot of core.
Make sure that you are doing a percentage of your running off road as this will help you keep up with the others.