How do i use rosemary essential oil and sage essential oil, for memory improvement?

No evidence: There is no reputable evidence on either of these interventions that they prevent brain cell death or improve brain functioning. That is not conclusive evidence that they do not help. However, there is no plausible mechanism of action that would explain why these interventions may help.

Maybe not the oils: Using sage essential oil for this purpose may not have much evidence, but using sage extract (salvia officinalis) may have some benefit. http://tinyurl.com/q76w6s7 there are very possibly some cognitive effects with rosemary oil: http://tinyurl.Com/pggj5m9 you could place a drop or 2 on some cotton and inhale gently; also there are air diffusers for this purpose.