This certainly sounds like quite a serious injury, and if you (or your friend) are not too sure about how to handle it, the best thing is to go to a doctor and let him or her take care of the situation. It is extremely important to get all the glass out of such a wound; glass that remains in the wound could keep tearing into surrounding tissue, making it very difficult for the wound to heal. This can also result in infection, complicating the situation. Even if the wound does somehow heal in spite of the splinters, there is a chance that the splinters will cause pain or discomfort later, at which point they will need to be surgically removed.
The kind of glass that is used to make bottles is often the kind that shatters when it is broken. This kind of glass can be quite dangerous - if your friend actually fell on the bottle, the danger is even greater, because the force with which they landed on the bottle could push the shards of glass quite deep into the tissue. Apart from the obvious result that the wounds will be rather deep, this will also mean that splinters may be lodged quite deep in the wound.
A doctor will be able to remove all the glass from the wound, as he or she will be more experienced and will also have better equipment. If necessary, the doctor will also perform an x-ray, which will be able to detect any remaining glass splinters in the wound. In any case, if the cuts are very deep or wide, they will need to be stitched up, and this should be done as soon as possible.
If the wound does not seem as serious as this, you can try removing the glass yourself, after which you should keep the wound as clean as possible. Sterilize a pair of tweezers over a flame for a few seconds, and then carefully pull out the glass splinters from the wound (make sure that your hands are clean before you do this). After pulling out all the glass splinters, wash the wound carefully, apply some antibacterial ointment, and then cover the wound with a bandage. Make sure that you change the dressing daily, or even twice a day if necessary. Each time you change the dressing; you should also wash the wound gently, and then reapply the ointment.
answered by G M