Bulk upload and sync issues Contacts and Companies

I’m new to Keap and marketing in general! I’ve been trying to get a list of leads for direct mail. I came across the following issues:

  • Bulk import of Contacts list and Companies list. Both with several Custom Fields

  • Inability to sync information in Contacts with Company Records

The objective is to

  • Find target organizations and information such as revenue, headcount

  • Find and add C-level Finance, Operations and IT contacts and their email, phone extn, LinkedIn page

My problem is if I search and add all this information in a .CSV file, how and where do I import?