Bring in what you already have

Export your contacts from your current tool as a CSV file (every tool has an export button, usually under Settings).

In Tri-Gig open Customers, then Import. Choose the file. You see a preview and can match each column to a detail before anything is added. Duplicates by email are pointed out.

Lists you added yourself can import the same way from their own page.

If an import was wrong, open What changed in AI Studio and undo it.