I would start by walking 10 minutes and gradually increase to 30 minutes (maybe 2.5K). Make sure you cut long toe nails and wear comfortable shoes or you will give up as soon as you start! After you are comfortable walking a reasonable distance, you could try jogging for 10 minutes and so on upwards. Personally, I have preferred jogging on my own but I can see how group activity suits many people. If you have a friend who has a similar target, why not do it together?
I started gentle jogging about 15 years ago and, at 64 years old, found myself running the London Marathon in 2011 and many half marathons since. Who knows where your jogging journey might end?
By the way, the support you receive on race days is usually great. It makes all the training worthwhile.