In fact working/meditating with chakras is considered to be advac=nced yoga technic, so basically I advise you to start from the scratch and do pranayams (breath exercises) for 2/3 weeks and later you can start meditating on objects or flame to enhance your concentration abilities. Having done this (2-3 months) you can go with chakras, but bear in mind that in meditation like in any other acitvity you should follow safety arrangements