I have 2 items in my inventory that say "... costume piece is unlocked... take to tailor" ... well I've visited the tailer and I still have these items in my inventory. Why can't i just click on them and it credits me? What am I doing wrong, i want to make sure those pieces are unlockied.

As soon as you wear them the costume piece is unlocked.

Unlocked pieces appear in a chest in the costume creator, assuming they are something you can actually use.
For example nearly 35% of quest rewards appear to be sword costume unlocks, which only 8ish% of the player base will ever be able to use, assuming frameworks are equally picked.

Yup you basically have to go to the costume vendor, and click on the "chest" tab, and at the bottom of the list, it will tell you what you have unlocked, and where you can find them :).

To be honest its a pretty neat idea to distribute new costumes, but I wished the unlock would happen on a account basis, so that any new characters made would have access to those costumes aswell.

Your bouncing avatar is very annoying, just saying.