You can upgrade it through either the Microsoft website or through a physical copy.
To upgrade it through the Microsoft website go to http://www.microsoft.com and look up at their Windows section, there you can download the version of Windows you want if you haven't already, and then install it. They have provided all the instructions on how to upgrade it, and also include some softwares to help check if your computer can be upgraded to the version of Windows you are looking for.
The steps are kind of different for every computer, so I would recommend you to read the instruction from the website, it can check your computer's compatibility and all the necessary details and can provide you the instructions you need for your individual computer.
They also have instructions on upgrading the version of your Windows through a physical copy, which you can look up for.
As the instructions are kind of different for every computer, it is better to look up the instructions at the website rather than typing it out here, as the details of your computer needed to determine the instructions are not known here, so look up at the website, you can find all the information you need to upgrade the version of your Windows.