Open KMobileTools from the Kmenu -> Utilities

When opening KMobileTools for the first time it might complain that it can't find the phone and that you have to check the settings.

Press the “OK” button and the Settings window will be displayed as shown below.

Under Mobile phone device enter /dev/ttyACM0 as shown above. Most mobile phones are picked up as ttyACM0 but if this does not work enter the correct device (if you don't know look on the KMobileTools website or documentation for directions). You can leave the rest of the settings at their default values as they are most likely correct. Now press “OK” and KMobileTools should show some info about your phone as shown below.

If you see Battery level and SMS Information it should be working properly. To send an SMS from KMobileTools click on “New SMS” and the window below will be displayed.

In the Destination field enter the number that you want to send the SMS to and click on the “Add Destination” button. Enter your message in the message field and click on “Send SMS”. Don't forget to read through the documentation to see what else KMobileTools can do.