Ok, here's the long and short of it.
You have a SE account. For that you are registered. But, if you try to go to the ffxi website or lodestone website, they may not be SYNCED. When this happens you only need to put your SE info to go to the websites.
However, since you didn't mention exactly what it was you were trying to do, like log into a certain website etc., its hard to give you a step by step.
So, what are you trying to Register for?
Name: Ghost Orchid - LEVEL 50 Bard, BLM, WHM, SMN Craft Level 7 Lucis, 6 4-star crafts: CUL, MIN, Wvr, Bsm, Gsm, Arm, Lth, Crp (Fishing and Alc at level 50)