APT can control Canon compatible lens when they are attached to Digic III or latter camera. Lens "Auto Focus" (AF) must be set to ON and you have to be in LiveView mode. Don't forget to set your lens in manual focus (MF) mode before plan execution!
Note: Some lens could be still controlled in MF mode. Give a try with ours to see it works. Start the LiveView and use the buttons <<< and >>> to see if the the lens supports control in MF mode.
APT has its own automatic lens focusing that uses the Focusing Aid and FWHM (Full Width Half Maximum) or HFD (Half Flux Diameter) metrics to achieve better focus than the camera built-in automatic focusing which is not optimized for astro photography. The selection between FWHM and HFD is made from the Auto Focusing Aid panel. In the next few versions the Lens Auto-Focus will be fully integrated with Auto Focusing Aid.
To use Lens Auto-Focus, Turn ON the Lens control, turn ON Focusing Aid panel, make a rough focusing using the lens drive buttons and frame a star in the Focusing Aid panel. After that click on the “Start Auto Focus” button. The precision of the focusing depends on the precision of your lens drive. If you are not satisfied by the focus precision you can run auto focusing for second time or to try with manual control of the lens. It is recommended to use the LiveView Zoom x5 option.
The Lens Control is accessible from 
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