Around 2 years ago my weight was at 89kg, which was definitely over-weight given my height and muscle mass. Like Bowen pointed out, weight alone isn't a good indicator of obesity since muscles (that weigh more than fat) need to be part of the calculation.
In any case, I started dropping weight like crazy by eating too little and running too much. 4-5 months later I had reached a weight of around 63kg which was somewhat close to being unhealthy for my height. I had to gain some weight and muscle, reached 73kg, began dieting/exercising properly unlike before and dropped to 69 where I'm currently at. Because I was too eager to lose weight quickly I ended up wasting a lot of time before I could get the slim body I wanted.
Much like Swalter said, you need to lose weight in a slow, controlled manner. 1kg is approximately 7000 calories, so if you start living with a calorie deficit of 500 calories per day (which is the recommended amount) you'll lose 2kg per month. You can achieve this by eating healthier or exercising but preferrably a combination of the two. Measuring calories in everything you eat is really boring, but necessary, unless you trust your ability to make decent estimates on your own.
It's really easy to lose your motivation if you don't see any results. Most people don't really notice any results after weeks or even months of dieting/exercising but that doesn't mean their change is non-existant. Make a habit of getting yourself weighed and your stomach measured weekly, before breakfast. If you keep exercising/eating healthy you will begin to see results very quickly, perhaps not with the eye but with other means of measure.
I won't delve into more details now, but if you need more advice you can always PM me. Good luck with everything!