There are numerous ways in which to access your chakras. From breathing exercises and meditation, to exercise and energy work. The point is unblock anything preventing the free flow of energy to and from the body.
The chakra system begins at the base of your spine and works itself up to the top of your head. Other chakras are located at the navel, the solar plexus, the heart, the throat, and between your eyes. Each chakra has a specific name and focus (for example Manipura is the chakra located at the navel and has to do with energy, determination and emotions).
While some people use seated meditation to access these energy centers, this Livestrong article addresses which yoga poses are most helpful in freeing stuck energy.
Chakras are energy centers in your body thought to represent various aspects of health and are associated with yoga and other Eastern philosophies. There are seven generally recognized chakras and the energy is thought to move through them, going from the bottom to the top. Chakras come with the belief that a blockage in one or more of them can cause health problems. While certain aspects of yoga, including alternate nostril breathing and meditation on the chakras are thought to open and unblock them, a number of yoga poses are believed to do the same.
Read which specific yoga poses correspond to which chakras here.