How do I get iOS 14

The same way that you have gotten any other update. You Goto Settings>General>Software Update and then follow the directions that come up when you go there. If you get a message telling you that it can't download for whatever reason, then it will tell you why and you'll have to follow those directions to get it to download.

go to "settings app" then to "software update" then press ''download and install" type your "password".

1. Go to Settings > General > Software Update.
2. Tap Download and Install. 

You can refer to this website for the detailed steps in upgrading to iOS14 below:

How to update to iOS 14