Adding of new Custom tab or updating of existing custom tab

Hi Advanced Collections Gurus,

In the below screen, you can see that there are two tabs (Custom1 and Custom2) provided by Oracle.

Our requirement is to add the below fields under Custom1 and Custom 2. Once these fields are made available, users will manually enter these details for each of the customer.

Primary AP Contact
AP Contact Name
AP Contact Title
AP Contact Phone
AP Contact Email

Alternate AP Contact
AP Contact Name
AP Contact Title
AP Contact Phone
AP Contact Email

How can we update the existing custom tab or creating a new custom tab with the above fields?

Regards,