What i found out that helps new players getting into the game, is having them take a look at the "Beginner's Guide to Eorzea". They added screenshots to the guide, which should make it easier to navigate through the steps required to set op the game.

Final Fantasy XIV - A Beginner's Guide

They added a section to the guide where the player can say that they've installed the game but do not have an account yet. It will take you through the steps to create an account via the launcher and enter your registration code.

If the game has been installed, a Square Enix account has been created and the registration code has been entered, but you still need a subscription in order to play; You can find additional information on how to register a "Service account" in the MogStation or find information about how to renew/add a subscription to your account (search keyword: "service account").

Final Fantasy XIV Support Center

I hope this helps.