Basically just use the media creation tool, it's all easily explained on the microsoft page:
http://windows.microsoft.com/en-us/windows-10/media-creation-tool-install?ocid=ms_wol_win10
Some tips before doing your upgrade, grab Display Driver Uninstaller, as your graphics drivers may not work off the bat:
http://www.guru3d.com/files-get/display-driver-uninstaller-download,20.html
And also grab the WINDOWS 10 version of your graphics driver, don't use any auto detect, manually select and download the driver for your GPU for Windows 10:
http://www.nvidia.com/Download/index.aspx?lang=en-us
http://support.amd.com/en-us/download
When upgrading your computer, you'll be given the option on what files you want to keep. Your 3 options will be.
Keep apps and documents. (everything basically, only your old windows goes away, everything else will stay and still work)
Keep only documents. (only your docs and media files)
Keep nothing. (This performs a clean install)
After upgrading your old CD-Key/Product Key will be different, you can use various system information/diagnostic software available on the web to find out exactly what it is. I recommend Belarc Advisor www.belarc.com/free_download.html (it will scan your system then make a local HTML document (webpage, but it's not on the web don't worry) and down in software licenses it will show you your new product key. It also still thinks windows 10 is windows 8 for now, but don't worry)
http://windows.microsoft.com/en-us/windows-10/media-creation-tool-install?ocid=ms_wol_win10
Some tips before doing your upgrade, grab Display Driver Uninstaller, as your graphics drivers may not work off the bat:
http://www.guru3d.com/files-get/display-driver-uninstaller-download,20.html
And also grab the WINDOWS 10 version of your graphics driver, don't use any auto detect, manually select and download the driver for your GPU for Windows 10:
http://www.nvidia.com/Download/index.aspx?lang=en-us
http://support.amd.com/en-us/download
When upgrading your computer, you'll be given the option on what files you want to keep. Your 3 options will be.
Keep apps and documents. (everything basically, only your old windows goes away, everything else will stay and still work)
Keep only documents. (only your docs and media files)
Keep nothing. (This performs a clean install)
After upgrading your old CD-Key/Product Key will be different, you can use various system information/diagnostic software available on the web to find out exactly what it is. I recommend Belarc Advisor www.belarc.com/free_download.html (it will scan your system then make a local HTML document (webpage, but it's not on the web don't worry) and down in software licenses it will show you your new product key. It also still thinks windows 10 is windows 8 for now, but don't worry)