No, you do not need a paid account, but the character has to be at least level 10. Otherwise you don't show up.
To make an armory link in TI:
1. Go to
World of Warcraft.
2. Search for the character (you can sort list by realm or level to make it finding it faster).
3. The default is a simple layout, but if you want to show more info click on "Advanced".
4. Once on the desired character page, copy the contents of your browser's address bar to your clipboard (or whatever the hell the kids are calling it these days).
5. To make a link like the one in my signature. I typed the word "SUPERVILLAIN" selected it, made it bold, changed the font, changed the color, and then (making sure my name was the only thing selected) clicked on the the little Globe icon on the TI word processor bar (it has a little thing that looks like a popcan opener on it, but it's supposed to be a chain link).
6. Paste the link you copied into the dialog box.
That should do it. If you want it in your TI signature, go to Edit Signature in the Settings menu.
edit: lol. Lil' and I must have been typing at the same time. i r teh slow typer.