There are three different ways to bring a contact into an occurrence of Contact Manager.
Leads
Use a webform to collect new contacts or update existing ones. Learn more about this here.
Importing
Use Data Manager's Import tool to quickly bulk import Contacts. Learn more about Importing here.
Manual Adding
Use the Plus icon from the Contacts listing:
Or the Triple Dot menu from inside a Contact:
to manually add a new contact. Learn more about filling in specific Contact fields here.