Update: If you don’t even have an extra monitor, you are still able to extend your monitor with your old laptop !! to do so, follow in link below:
Today, using multiple monitors is almost a must. However, If you are using more than one monitor at home or work, you may prefer to switch the priority between them to assign it as the main monitor. to do so, follow quite simple below steps (or your can follow steps described in following video);
Right click on any blank area on your desktop and select Personalize and press Display at the left down corner. On the left upper side menu, select Change display setting. Now you can see your monitors. Just select the one that you want to be as your main monitor and check the Make this my main display box.