To change settings for your screens, right click on an empty location on your desktop, and select “Display Settings”, you will get a menu to allow you to re-arrange your monitors and to choose which ones to display on. There is also an option here to set which screen is your "main", or the screen that shows your login, and where your start menu pops up.
For quick changes, you can use the shortcut Window Key + "P" to open a side menu where you can make changes to external displays