My only tip is to do what he said - make healthier choices about what you're eating. To be honest, it's not that difficult to tell which foods are best for you, the issue here is having the willpower to reach for the fruit instead of the chocolate.
Saying that, fruit has more sugar in it than you know. It is natural, but too much could be dangerous for you, so try not to eat more than one or two servings per day. Try to get most of your 5 a day from vegetables.
Drink plenty of water
Try not to set yourself unrealistic goals for weight loss. In fact, don't even think about the weightloss, just focus on being a healthier version of yourself, and the weight loss will happen.
If you're going to exercise, start of slowly, maybe 10 minutes every couple of days, so that you're not doing too much to soon, and then slowly build on that. Or try something lighter like Yoga to begin with.
What worked for me when I started trying to be healthy was the 30 Days of Yoga challenge with Adriene on YouTube. I did that whole 30 days, and then started introducing cardio every couple of days as well. I also did not think about dieting. I found just exercising gave me the confidence and awareness to instinctively start making healthier choices about food.
i am not diabetic, or close to it, but both my mum and nan have / had the condition, and complications with it. To be honest, what made me think about being healthier is the state my mum is in now. She's diabetic, has high blood pressure, has had a stroke and is currently undergoing dialysis. The sad thing is, she never looked after herself. If she had, all of this could have been prevented. If that's not motivation to be healthier, I don't know what is!