Walk walk and walk. Then, when you're comfortable, add in some bits of running. Then, increase your running time little by little. I highly recommend downloading a tracking app such as Strava (total motivator for me). Don't change too much about your life all at once, even if you feel super duper motivated right now. It WILL backfire later - it's happened to me several times!

Also, after a lot of experimenting and dealing with different types of failed attempts at spot reducing (I've always had flubby upper arms and a huge lower belly gut), I've learned that the best way to target them is through slimming down your entire body with cardio and watching what you put in your mouth. Only when I lost weight all over my body did I see any results in my arms and belly!

Hope this helps a little, good luck!