The short blogs shows you one of the ways to upgrade from Visual Studio 2017 15.0 to 15.2.
Click on the small flag at your right top corner then you will see “Visual Studio Update” is available. Click on it.
When you see another dialog pop-up then click Update.
Then it will ask you to close your Visual Studio if you have not.
Once you close your Visual Studio 2017 then you can click Retry and your upgrade will start. It took me around 1 hour.
You can then launch your Visual Studio 2017 15.2.
It is Version 15.2 now.