Read the instruction book!
See how close you can get to the item per that book (in macro mode, if it has one). Anything closer than this will be blurry.
If you can’t get as close as you’d like to, take the highest resolution photo you can from the minimum focusing distance and then crop the photo.
Here’s how I’d do the lighting. I realize I’m kind of beating this to death, but I find that shiny objects like coins are real hard to photograph well (at least for me).
Turn off the flash and set up a couple of lights to illuminate the coin. One should be stronger than the other. I’d put the brighter one at about 2 o’clock and the weaker one at about 9 o’clock. Possibly use a white handkerchief over the lights and/or use redirected light (bouncing it off, say, a white piece of paper) to reduce glare and to adjust the intensity of the light. You can also move the lights further away to make these adjustments. Keep the brighter of the two lights a little low along the side of the coin to increase the shadows on the coin and make the markings more visible. Use the second, weaker light for fill – that is, to reduce contract and soften the shadows a bit.
In addition:
You might do better adjusting the focusing manually, if your camera allows that.
If your camera allows exposure adjustments, try adding or subtracting stops if the photo is over or underexposed.
Bottom line, though, is that you’re going to just have to experiment, which fortunately is pretty easy with a digital camera.
Hope this helps!