Press 1 2 3 4 after a vowel (a e i o u ü) to add the 1st, 2nd, 3rd or 4th tone mark to it. Press the key again to type the digit 1 2 3 4 instead. To type ü, press Alt + U.
Stop the mouse over each button to learn its keyboard shortcut.
Shift + click a button to insert its upper-case form. Alt + click a button to copy a single character to the clipboard.
You can select text and press Ctrl + C to copy it to your document. In your target document, press Ctrl + V, or, if you want to paste the text without formatting, try Ctrl + Shift + V.