In looking to the timing diagram ( **broken link removed**) it demands a 10us input pulse to start operation. An output port needs to be connected to this Trig-input of the sensor and the Echo-output needs to go to a micro input port. The 10us start pulse you need to create by a timing loop or a timer. The length of the pulse returned is equivatent to the distance (formula in the paper). Again the pulse length can be measured using a timer which starts on the raise of the echo output.
Enjoy your design work.