also if you really want to use reiki just as TaskRushh said you need an atunnement, but there is not need to go yo a reiki master i can teach you (Mikao Usui didn't attune to reiki with someone's help he did it alone) and there is not need to worry it won't take long though there is something that i must tell you before attuning try to keep the consumation of: meat, cigarettes, sweets, soda etc to a minimum or if you can just don't consume them at all for a week this usualy takes a hole mounth but for me it worked fine even if i just did it for 3 days (doing this will help the energy meridians which are spread along your body to open even widely which will result in a better energy circulation)
Now for the meditative part, this is next after the diet
-sit confortably you can just lay on your back, take the lotus position or you just sit in a way that you feel is ok 4 you
-now concentrate on your whole body and imagine roots growing from you and spreading through the ground, try to visualize them spreading as much as you can after you do that try to visualize them being connected to a sphere of light, that light is the soul of this universe now use the roots which you spread to absorb energy from the sphere, after doing that well you just becomed attuned to reiki.
Though it wont work if you don't have someone to teach you the hand positions, there are hand positions for all the body areas, though they are divised on two categories hand position which you can use them to heal yourself and hand postions which can be used to heal someone.