Whatever you keep your contacts in, the path is the same: export a CSV, drop it in, and check what it found. Ten minutes once.
- Export a CSV from wherever your contacts live. Every CRM can do this: Follow Up Boss (People, select all, Export), kvCORE (Smart CRM, Contacts, Export), Lofty (CRM, Leads, Export). So can a spreadsheet or Google Contacts.
- Drop the file into FOLLOWap in Setup › Bring people over. You see a preview of what it found before anything is saved.
- Check the report. It tells you how many came in, how many looked like duplicates, and anything it could not read.
Names, phones, emails and the street address with its ZIP are what matter most: the address is what matches a client to a sale nearby. Column names do not matter.
Nothing is ever deleted by an import, and bringing the same file back fills in blanks rather than overwriting what you typed.