Crikey, over 50 views and no responses? Here's a handy step by step guide.
1. Mount lens on camera and remove lens cap.
2. Switch camera on and put into AF mode.
3. Select a suitable target and point camera at target.
4. Press button to activate AF (shutter release, or AF-ON, or whatever you generally use on your camera).
5. Take picture.
6. Examine photo to see whether it is in focus.
7. Repeat from step 3 as required.