The Sending training shows you words and you have to send them using either actual hardware key or paddles hooked up to your phone or using the on-screen key or paddles. When you can send enough words correctly, the speed increases. When you make to many mistakes, the speed is reduced again.
The screen is pretty simple. In the big space in the middle, text is shown that has to be sent. In the button row at the bottom the sending can be done: (1) is the speed setting. You probably guessed it: The „-“ button will decrease the speed by 1 WPM, the „+“ button increases it. The number shown between these buttons is the current speed in WPM. (2) is the on-screen paddle. „L“ is the left key, „R“ the right one. Of course this is just a contingency key. You can also hook up an actual key to your phone using USB and use that for sending training. The other thing to note is that you can configure Dahdidahdit to use a straight key. This will affect both this on-screen key and the one connected using USB.