As this lens requires you to manually adjust aperture, Av and Tv modes will be useless to you. Manual mode is your only option.
To adjust aperture, you move the aperture ring on the lens. This ring is marked with the different f-stops. This will be obvious when you actually are holding the lens in your hand. Despite having to manually adjust aperture, your camera will still be able to meter correctly. The only difference is having to adjust aperture using the ring on the lens, instead of on your camera body.
Focusing should be self-explanatory. For such a wide angle lens, use a tripod, and LiveView. A good rule of thumb for focusing UWA is using LiveView, magnify 10x at about 1/3 of the way into the frame. At such a wide angle, most everything is in focus, and you will find it difficult to determine where critical focus is. This will take some practice, but using this general guideline will help a lot.