Assuming that with the "latest version" you mean the 1803 version released this week, download the .iso from https://www.microsoft.com/software-download/windows10 , mount it and run setup.exe. That should be all.

The time to download depends on the speed of the internet connection, the time to do the update depends on how fast your PC is. A time of 1 to 2 hours is reasonable. Don't interrupt! If it's a laptop run it with the power adaptor!