Custom CRM Fields, more

Custom CRM Fields, more

I'm in the CRM - Contacts

1. In Home / Customization / Modules List:Contacts
  It shows MODIFIED BY field. I hit save. But this field does not show up in individual records, in Contacts. Why?

2. I need to create 2 new fields, for Contacts.
What steps do I do to make these 2 fields, 15 char length each.

Field names:   "Contacted Date",  "Modified Date
"