This is a common failing with digital cameras, personally I always buy one with and optical view finder as well.

But all is not yet lost, go through the menu setting on your camera, you should find something like camera setup. Look for LCD set up an the adjust to the brightest setting.

After that, you're into camera upgrade country, although some years ago, I did see one camera with a clip on sunshade which helped. Or you could just try cupping your hand over the LCD that also sometimes helps.