Go to 'Start', then 'Control Panel', then 'Appearance and Themes'. Then, under the heading 'Pick a task', click on 'Change the screen resolution'. On the 'Display Properties' window you will see a section that says 'Screen resolution'. Use your cursor to drag the bar so that you can select your chosen screen resolution.
If you wish for things to be displayed better on your screen, then selecting something like 800 by 600 pixels may be the best option, whereas 1024 by 768 pixels will give a smaller display.
Another option that you can select in the window is the colour quality, although this cannot be altered on some laptops. There are other options that allow you to alter your monitor, but you refer to your instruction booklet for these options, as that will give a detailed description of what each option does. There is a troubleshoot button in the 'Display Properties' window that will help you with any problems.