Go to the main menu of your phone. In any of them there is an item "Settings" (usually depicted in the form of a wrench) in which there is a tab "Screen" or "display Settings".
Select "full screen" or "display". Usually in this menu item you can select the time after which the screen will go blank and will start the screen saver, as well as the image that will be used as it. Choose what you like from a standard phone gallery or set as a screensaver self-made photo (or even a few of them: many phone models possess the function to automatically change photos on a screensaver).
Try to install the screensaver differently. Go to phone menu, then navigate to "Gallery" or "file Manager". Choose a picture and start menu Options. Usually it is one of the keys to the bottom of the screen. In the menu, use the "Choose image" and then select "Use as screensaver". Now the selected picture will appear on the phone as a screen saver after some time after disabling the display.
Set as Wallpaper any image from the Internet, if you are not satisfied with the standard image from the gallery. The downloadable images must be in the format *.JPEG, or *.GIF (if your phone supports animated screensavers). Use any of the search engines to find a website with suitable images. If you went online with your phone, it is enough to save the picture in the device memory and you will be able to use it immediately from the menu "Gallery". If you upload an image to headband from your home computer, then use the special USB cable that comes with the device to move the proper picture or a few of them on the phone.