@daphine2004 well done on starting - that's the biggest barrier overcome already!
Are you using the official NHS podcasts/app from the NHS website? Because their are many copies and you won't get as good coaching and training tips as you do from the official one. If you're a total novice I'd recommend the podcasts over the app - the running music is then specially designed to match your expected running pace:
www.nhs.uk/Tools/Pages/Couch-to-5K-running-plan.aspx
And on the subject of pace - slow down
Assuming you're doing the eight 60 second runs of Week 1, if you can't finish all of the runs then the only reason for this is that you are going too fast.
You are capable of running all 8 florets hose 60s runs in full - right now at your current level of fitness (or unfitness, if you think that way). You are not too unfit for it. Your body can do it and can do it fairly easily. Two things are in the way:
(1) your mind
(2) your speed
The next barrier to overcome is your mind telling you that you can't do it. Because your body IS DEFINATELY capable of running 8 lots of 60 seconds (and more). But you think you can't, so you give yourself permission to walk instead. You can do it though, you really can.
How? Slow down. The only physical thing that could stop up is that your run is too fast. You are looking for a very light jog. Do a running motion but take your pace right down. Go slower, plenty slower, than you think you need to.
Keep the run (jog) going for the whole of the 60 seconds but keep yourself going slowly. Keep all eight runs slow paced, but it's important that you run - don't walk - all 60 seconds of all eight runs.
The way to do that is to slow down.
Slow right down.
Go much slower than you think you need to. Light, light, slow paced jog. This is what you're looking for.