Each client becomes a portal record matched to their email. They do not need a password from you... they create their own when they register on the portal with the same email you have on file. Their collection and session date will already be waiting for them.

After importing, tell each client: "Go to the portal, click Register, and sign up with this email. You'll create your own password."

Expected columns (header row required): First Name, Last Name, Email, Collection Name Only, Session Date. Extra columns like Contact Id are ignored.