Just follow these simple steps:
1. Open the Command Prompt / Terminal
2. Type the command in the following format :
Editor fileName.fileExtension
As shown in the example on Figure 1 below, we used Notepad as text editor. So we came up with the command :
notepad test.txt
Figure 1
3. Press the Enter key.
Figure 2
4. You'll be shown with a popup message asking you if you want to create a new file. Just click "Yes" and you're done!
Figure 3