Adding field input to a field I am creating a custom content type with the following fields:


  
  Name
  Offices(can be many)
  Address(offices address)
  


Question is, how can I be able to add address field to each office names?
Sounds like you want Paragraphs or Field Collection.

Basically, the idea with these modules is to group two fields (office + address) as a set within an entity and then embed that entity in your content type.

For Drupal 8, Field Collection recommends using Paragraphs, so that's the module I would use.  For Drupal , I would use Field Collection.