How to add "login ID" on Contacts?

How to add "login ID" on Contacts?

Hi,
 
Sorry if the question seems basic, as i am new on using this SupportCenter Plus.
Cant seem to find the way on how to add "login ID" for my newly added contacts.
Only details required for me to input are:
--Name
--Email
--Alternate email
--phone
--mobile
--twitter screen name
--job title
--account/sub account
--Primary contact (uncheck or check)
--description
using Version: 7.8.0
Build #: 7804
Appreciate the soonest help.
 
 
 
 
Version : 7.8.0
Build Number : 7804
 

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