Funnily enough I don't think we have an FAQ to do with this.
It's a long and complicated process my friend, but I tend to split it up into two phases: during the first, you must select all the addons you wish to use. (Some of these are likely to change during the course of your designing, but as long as you have decided on the main ones, you'll be fine.) To help you with this I would suggest using
Vranx, a website which has a list of good addons for any purpose. Once you have an addon for each of the main sections in the list (UnitFrames, Chat, Minimap, Buffs/Debuffs, etc), you will then enter phase two, which is basically entering the game and configuring every single addon to exactly the point you want it. Obviously I can't tell you how to do this right now, because every addon does this in a different way, but you'll usually start by typing the addon's name preceeded by a forward slash in the editbox - for example, to configure Pitbull, you would type '/pitbull'.
To change the font, you'll need at least one .TTF file (up to four) and you will need to create a folder in your World of Warcraft directory called 'Fonts'. Inside this you must place up to four font files (if you only want to edit one or two or three of them, that's fine, the other font/s will still be left as the default ones):
- 'ARIALN.ttf' - The font used in the chat box, info panels, etc.;
- 'FRIZQT__.ttf' (Yes, that is a double underscore, don't miss it) - The font used for the names of NPCs, items, spells, etc. and used on most interface buttons;
- 'Morpheus.ttf' - The font used for quest log text and mail text;
- 'skurri.tff' - The font used to display critical hits in Blizzard's default combat text.
Don't get frustrated if it takes you forever or something doesn't work. If you think an addon just isn't doing what you want it to, or it doesn't suit you personally, then uninstall it and try a different one from
Vranx. That website really is a saviour in terms of deciding which addons to use, especially for beginners.
Good luck, young one!