It describes the remedies and their actions on the body in detail. Read about the remedies that show up most often for the symptoms you've listed. When you find what seems to be the most suitable, administer it. This is a 'dose' three times a day for three days, or until the symptoms change. At that point you would change the remedy.
Homeopathic remedies are non-toxic.
If you administer the wrong remedy, there are no ill-effects. You just won't see a change in the symptoms. This is not as complex as it sounds, and can be simplified with the purchase of a good book on homeopathy in the home and a small kit. Some are sold as children's kits, with 8 remedies. Another kit has about 35 remedies in it.