How can I enter notes with my computer keyboard?

If you want to write music with your computer keyboard:
Use the mouse to select the value of the first note.
Then move the cursor away form the score.
The cursor turns into a red circle-backslash symbol: the "no" sign.
Let go of the mouse.
Now the keyboard is activated.
Write your music with the computer keyboard.
The keyboard's layout is here:
Help -> Keyboard Layout.

If you want to switch from "Easy to Use" to "Touch Typing" or vice versa, go to main menu "Options" - "Workspace".