Helping New Players
I just bought the game off Steam and managed to get into my account, and I wanted to leave this post to help anyone else who might be confused like I was
POL Registration: I think this was the easy part, personally
-Username: Just made the same as my SE ID (example: Buttz4)
-Nickname: Whatever you want (example: Bartz)
-POL ID: 4 Letters, 4 Numbers (ABCD1234)
-POL Pass: Set to 'Save', doesn't use !?)", so keep it simple or close to something familiar (example: ApplePie)
-Member Pass: optional, for personal account if multiple people use your computer
-Square ID: Important, binds to your SE, same one you use for 14 and MogStation (example: Buttz4)
-One-Time Pass: Use it if you got it, I don't so
Once you finish that, head to Squares Account Management site and go to the FF11 Page, add your game to your account (Add Service Account), use the CD Key Steam gave you (Click the Gear on its Library Page or Right Click the game, Manage, CD Keys. Sometimes these can be in Properties too so check around just in case)
After that, Square should give you a bunch of new information about your account, there are options to change those settings at the bottom of the page like POL Password, POL Email, etc. The most important details are the POL ID and Password, Square will give you a completely new ID and Password, you can only change the password.
Back on the Launcher, change your ID and Password to the ones on Square's Account Management page (so your new POL ID: DCBA4321, POL Pass: l33tHax0r (or whatever you change it to, like ApplePie))
Then, you select your account (Bartz), make those POL changes in the Settings first, then Log In. It will ask for your Square Password, so make sure to use that one. Some folk say it helps to use the in-launcher keyboard to type it in instead of manually or externally, so try that if something goes wrong there.
Now you should be in the POL Browser/Home Page. It'll ask you to make a Handle/Username and agree to some services like all stuff does. Make any Profile Adjustments you want and then click the Crystal to boot up FF11.
[Important]
If you try to boot up 11, it will say your account is expired or non existent, that just means you don't have an active subscription. Go back to Square's Account Management for 11, click the button next to Characters and it will take you to the Subscription set up stuff. Your first Sub is 1 Free Month, so just add your Payment Info like normal and it will wave the fees at the end.
Return to FF11, preferably after resetting the Launcher, and sign in again.
After the game updates, now that you have a fresh Sub to play with, have fun.
This took me a good hour of browsing different reddit posts and feeling like a complete stooge when I realized what I was doing wrong. So I hope this helps.
If there's any issues or something I left out... I forgot or didn't experience that, so I hope someone has the answers you need like I did.