If your iPhone screen is all white and won’t show any icons or the Apple logo or anything else other than white then you aren’t going to be able to operate it until you’ve fixed whatever issue caused the white screen. The first thing to do to try to fix this is to restart your iPhone by pressing on the Hold button at the top right of the iPhone until the red slider appears, then slide that to turn the iPhone off. Wait for two minutes and then turn your iPhone back on by pressing down on the Hold button until the Apple logo shows up.
If restarting your iPhone didn’t make the white screen go away, then you might need to reset your iPhone. To do this, hold both the Home and Hold buttons down at the same time until the Apple logo appears. If that doesn’t fix the white screen issue then you will have to try to restore your iPhone from backup and you can do that by connecting it to your computer and going through iTunes.
If restarting, resetting or restoring your iPhone hasn’t helped and you still have a white screen you will have to call the Apple Genius Bar or go to your local Apple store to see what the issue is and get it fixed. If it is under warranty this may be covered, otherwise there might be a fee.