I have a hp pavilion and every time I go to windows photo gallery,choose a picture,the print screen pulls up with the picture and I can't see the bottom of the screen to click print.. I've tried to go in control panel and change display moniter but it won't let me see "apply,cancel or ok" to click on either

You probably tried this, but, right click on the desktop and choose "screen resolution" and set it to the highest setting that's shown. If you are then asked to confirm the setting, choose yes (assuming the screen looks right). This menu option is available in specific versions of Windows and may not be in yours. You didn't specify your version.

Also, many windows will allow you to re-size them yourself, and will remember what size you chose when they restart. If yours is that way, you can move your mouse to the upper edge of the programs window until it changes to an up/down arrow and left click drag it down. Once you have shortened the height of the window you can grab the top bar of the window with a left mouse click and drag the whole window up to see your buttons.

Try right clicking on the upper right corner of the Window and select Move. Then use your cursor keys to move the window up where you can see the Apply button.