In order to be able to use Reiki, one MUST attend a Reiki class offered by a Reiki Master.  The Reiki Master must have (at some point in the past) undergone at least three levels of Reiki training with another Master. 

During a Reiki class, a student can expect to be taught about the history of Reiki, the origins of Reiki, the practical applications of Reiki in life, and in the body: physically, mentally, spiritually and holistically. 

You cannot gain access to Reiki energies without attending a class and undergoing an attunement process.  The attunement is a meditative ritual on the part of the Reiki Master.  The Master will perform the necessary processes upon the student, and the student will then be able to use the Reiki energies.  Although an attunement can be 'sent' over distances by a Reiki Master (many Masters offer internet courses where they will send an attunement), I discourage such practices for anyone who is just learning Reiki or just being acquainted with Reiki for the first time.  Nothing can take the place of working with a Reiki Master in person.  And personally, I just think that an attunement that is done physically is more potent.  Others will disagree with me, that's just my personal opinion. 

There are books out there, and video tapes out there that talk about "teaching Reiki".  Please understand that these materials are intended to be supplementary to actually attending a class with a  Reiki Master.  You cannot learn to do Reiki by reading a book, or by watching a video.  ONLY a Reiki attunement can enable one to use Reiki energies.