You can manually start the upgrade process by using the media creation tool..
Contrary to what the program is called it can be used to manually start the upgrade rather than waiting for Microsoft to roll the upgrade out to you eventually.
Like any major install/upgrade process, backup any important personal files in the event something goes wrong (shouldn't but never can be too careful)
Download the version that matches the version of Windows you are running (64-bit or 32-bit) at
http://www.microsoft.com/en-us/software-download/windows10
If you don't know if you have 32-bit or 64-bit version of Windows do the following to find out:
- Press Win+E (that's the Windows Key)
- Click System Properties
- Look under System Type to see the type of system is currently running.