This is the British Army get fit leaflet version I used :
Get a pair of trainers you can run in. Not fashion trainers, actual trainers. Grab an old tee and some shorts or tracksuit bottoms. if you’re a girl over an A cup, get a sports bra.
grab your phone or a cheap digital watch. Something with a timer of some sort. There’s a lot of free running apps too that will track your distance, but we don’t give a shit about that until week three.
go out your front door. jog as far as you can and then walk the rest of it for four minutes non-stop. Stop for breath. walk back. (you’ll be tomato faced and wheezing and want to die. this is normal.)
By the end of the week, try to increase this to 8 minutes. Stop. Get your breath back and stretch a bit. Try and jog bits of the walk back, but keep moving, even if it’s at snails pace. (it’s normally add one minute or one block per run). Don’t do it every day. If you only increased it by two minutes, that’s fine. You’re still making good progress. A really good way? Pick a marker not too far in the distance like the next tree or lamppost, grit your teeth and get to it.
Week two. Try and make it to 12 minutes. Jog more of the way back. By this time, the blisters *will* be appearing. Sorry. You may want to start carrying water, especially if it’s warm.
Week three, sixteen minutes. By this point it starts to get easier and you’ll find yourself cruising past the old eight minute marker without thinking.
Week four, twenty minutes.
Week five, still twenty minutes, but increase the portion you jog of the way back.
Week six, jog to your twenty minute mark, hit it with your hand and turn, running as much of the way back as you can before stopping for breath.
You’ll hit 5k.
And remember: you may be slow but you’re still lapping everyone on the couch.