No early access code

[Kirika-]

Your Early Access begins June 28th, which you have already triggered via your Pre-order Bonus Code (ie. You entered that code when you pre-purchased the expansion and got your goodies; minion and earring).
So, on June 28th you can log in and start doing Dawntrail content.

On July 2nd, you can then enter your Full Game Registration code for Dawntrail (enter too early and it will say Invalid), which then switches on your account for post early access and you are now fully expansion enabled, and you can then continue from the point you left off during early access.