If your Windows Operating system Windows 7 , Windows 8.1 You can upgrade your Operating system to windows 10 for free.
If your Operating system is windows 8 , first you have to update your operating system to windows 8.1 then you can upgrade your operating system to windows 10.
Please access the above link and download the upgrade tool. Tool will be installed on your computer . In that window , we will have two options
1. Upgrade to windows 10
2. Create windows 10 Media
Kindly go ahead with Option 1 and the proscess will take 2 hours . During the proscess, your computer will be restarted many times.
Incase of any problem , Kindly reach us , we will help you to solve your problem.