All merit badge counselors should complete a new BSA adult application, indicating "42, Merit Badge Counselor" in the position code and position description block. There is no registration fee to become a merit badge counselor.
If you are a currently registered BSA adult member, you must still submit a separate application to become certified as a merit badge counselor. You may print a copy of your Youth Protection certificate from myscouting.org. If you are new to BSA, you must follow the instructions in the ppt below to complete the online training.
Finally, new merit badge counselors must complete a Merit Badge Counselor Information Form indicating what merit badges you believe you are qualified to counsel.
A current list of merit badges offered and their associated requirements can be found at
http://www.scouting.org/meritbadges.aspx.
Additional materials provided below for your reference.