Add contacts to the Address Book of the persons you often share too. Go to the Sharing Menu. Select the Address Book. 
Select the “+,” and you will see this pop window where you can type in the credentials. Special cell number is essential if you want to share with “two-factor authentication,” where the recipient will receive an SMS text message with a 4-digit code required to access the share. Just type in the country code with “+” or “00.”