Joods!
I started running for the first time this year a few months back, (I'm doing a 10K this sunday), and have done a few 5K's.
For what it's worth, this is what I did. For background, prior to this I've never run at all really, and on my first day could barely run out of the car park of my work.
If you can try to run 2-3 times a week, each time just going at a steady pace for a long as you can. If you run out of breath or are tired, slow down to a walk until you catch your breath back/feel up to it, and go again. Start off aiming for around 1 mile in total disatance, and do this until you can do 1 mile in one go.
After that, you just need to start pushing yourself a little more every week. It took me around 6 weeks, but I was able to do my first 5K. It was hard, and I felt it for sure, but if you run at a slow pace (you don't have to gun it the entire time) you'll be perfectly fine. Since then I've done a few more 5Ks (we have a thing here called park run, and is a 5K every saturday morning) and have moved onto trying to expand as I prepped for this 10K.
Diet wise, just be sensible. You don't need to cut things out of your diet completely, but just think about it. Want a Soda? That's fine, but get a 0 calorie one. Keep eating what you like/want, but work on portion control. You will lose weight when you are burning off more calories than you take in. That's litterally it.
For me: I dropped sodas/sugery drinks completely and switch to water/fruit juice, and changed my lunch to flavoured rice, ensuring I was putting in a low ammount of calories into my body. I take protein shakes after running long distances to help with recovery, and also attend a Brazilian Ju Jitsu class once a week. Alcohol wise, thats up to you. For me I switched from full pints of beer to halves, and it worked out ok for me. If you drink wine, have a small instead of a large or just cut out alcohol all together, it's your call.
Since starting running some 19 weeks ago, I dropped a total of 20lbs from my starting weight due to the above. I'm back up a little bit, as I've not focused on the diet as much as I should, but I'm still 11lbs down from where I started, as I'm able to keep the weight off by running. Now shirts fit me that didn't before and I look/feel much better than I did earlier in the year.
But yeah, overall, just go slow and steady with runing and work up to a mile. From there, you should start to see the difference and have a good idea how to push forward/challenge yourself when you feel up to it.
Feel free to ask any questions or PM me for anything else
Quick edit to add: I don't go to the gym, everything I've done is outdoor running. My tip for that, put some shades on, and plug in some headphones. That way you can tune out of the world and focus on your running/breathing. Plus music can help you get into "the zone", as people say haha.
