Changing the screen size requires different steps depending on the operating system of the user's computer, but getting the correct resolution for a monitor is as easy as looking at the manual for the specific monitor and looking for the device's stated native resolution. From there, the user can typically find the options to change the monitor's resolution to the native one in the control panel of the system, and this should make the screen size fit the monitor.
Most modern operating systems are able to detect the specifications of attached hardware such as monitors, and the system either automatically defaults to the monitor's native resolution or at least recommends the appropriate setting in the control panel.
Instructions for changing the resolution for any currently supported Windows operating system can be found on the windows.microsoft.com support website. As of 2015, this includes all operating systems produced by Microsoft back to and including Windows Vista. In all cases, the resolution can be changed in the control panel under the display options.
Likewise, explanations for changing the screen size of Apple products can be found on the support.apple.com website. These options are most often found on the Display panel of the system preferences menu.
Other operating systems, such as Linux or a custom operating system, may require the user to consult the support of the specific system. The required technical knowledge of a Linux operating system may require the expertise of other users who run the same system. As such, consulting a user who already knows how to deal with Linux-based issues may be necessary to find useful instructions for adjusting resolution. As Linux distributions differ significantly, there is no typical case for changing resolutions on these systems.