Astrology is a very wide and complicated field of study. It consists of a spiritual science that uses the stars, planets, and astral bodies to provide the individual with self-knowledge and knowledge about the world. While it may seem a bit overwhelming to the beginner, astrology can also help to enhance your experience of the Tarot.
A good place to start is the birth or sun signs, as they relate to the Tarot cards. The site http://supertarot.co.uk/astrology/ gives some very good guidelins on this.
Some Tarot decks also include elements of astrology as part of their design. If you want to make the learning process easier, you can buy one of these. The Elemental Tarot and Celestial Tarot are good examples. These decks feature astrological symbols and a booklet of instructions on how to interpret these with the cards. This is an excellent way to start the learning process.