In this tutorial you will learn how to set your pi desktop to have the same screen resolution as the monitor or laptop you are using VNC Viewer to access your Pi with. The first step is to determine your monitor (laptop) screen resolution
Monitor screen resolution
In Window's 10 you go to Settings/System/Display (you can type "Change display settings" in the windows search bar) and scroll down to "Resolultion
Now that you know the resolution of the monitor you are using to remotely access the Pi, you can set the resolution to match that (1920x1080 in this case).
Setting Pi Desktop Resolution
Remotely log into your Pi and click the Raspberry icon/Preferences/Raspberry Pi Configuration (fig. 2)
Toggle to the Display option and you choose "Set Resolution" (fig. 3)
Choose the option of your monitor and click OK (fig. 4)
You will need to reboot the Pi for the settings to take place.