UPDATE: here is an email from a pharmacist it reads:

Applying a tiny amount often described as a lentil pea size amount periclitorally can help with sensation and orgasm. For systemic absorption to help improve libido, etc. most physicians will suggest applying to inner thigh or behind the knees. Typically the prescribing physician will specify an amount to apply and the timing of that application. For example, in small daily doses or for more concentrated prescriptions such as yours applying 1gm (1/4 tsp) twice weekly.


Assuming testosterone levels are low, most patients will continue hormone supplementation indefinitely or until their physician advises them to stop.