You have set the shutter speed or the aperture wrong. The aperture is too wide or the shutter speed is too slow. Basically, what is happening is that so much light is getting to the image sensor in your camera that the camera cannot decipher the details of the subject. If you are using auto mode, then your camera may be confused based on the lighting in the situation. It is time to switch over to manual.

To start with, check the shutter speed. This is the most common problem. All you need to do is raise the shutter speed a few clicks, and you should see an immediate difference. Since you are using manual on your camera to avoid the overexposed image, then you may have to take a couple of pictures with different shutter speed and different apertures until you get one that is no longer washed out. Be careful not to raise the speed too much or you may end up not letting enough light in and the picture will be too dark.

Example of washed out (or overexposed) image