Creating an appointment on a 2nd user profile calendar in outlook without having the main user as orgenizer

I have 2 exchange account. 

the main account has full access on the 2nd account.

The main account in outlook 2013 profile is the main account and it has an additional account - the 2nd account.

When I open the 2nd's account calender and try to create an appointment, although the participant is the 2nd account, the meeting orgenizer (the account which sends the mail) is the main account.

in the from tab I can't select the 2nd account.

How can I create a meeting in the calender of my 2nd account in which the 2nd account is the organizer ?

Thanks.