Where do absolute monarchs claim to get their power?

In most cases, through uncontested inheritance of the position (either from a parent or another relative upon their death or abdication). In some instances in history, the monarch gained his power through rebellions, wars or making a case of being a better claimant to the throne. Then, in the tradition of those he usurped, he would establish his own family dynasty of heirs to succeed to his position (research Henry IV, Edward IV and Henry VII of England).