If I Want To Use Herbs For Herbal Medicine At Home, Can I Use Dried Herbs?

As a general rule, you should always use fresh herbs for making remedies to be used at home.  This is because none of the essential oils and properties of the plants will have been lost in the drying process.
This does mean that there are limitations on what can be made at different times of the year, but dried herbs are much less potent and bearing in mind that hebral medicine is a very gentle form of medicine, you need all the potency you can get !
Herbs used for medicine should also be organic or best of all growing wild or in the garden.  If they are not organic and bought from supermarkets, they will likely have been treated with both pesticides and insecticides.  Moreover, they will not be as fresh as those which are picked from the plant and then made into a remedy on the same day.  
If it is not possible to grow herbs for medicinal purposes, you can buy herbal remedies from health food shops/herbal stores which may be equally as good.