OK here goes a small explanation than ;D
The tools you'll need if you wanna make only textures and not models are DePbo or OFP_Decrypter 1.5,StuffPbo or MakePbo,TextView,P3d_Utility and a good Graphis Program Paintshop Pro or Photoshop will do, perssonaly I use Photoshop, if you can't find them all in this website you'll find the rest in here
http://ofp.gamezone.cz/index.php?newlang=engIf you intend to make models than you need O2, and maybe 3D Max depending on the kind of models you wanna make, but let's say you'll do fine just with O2 at the beggining.
All this tools can be found in the Editors Depot from this website or in the link I gave you , all but Paintshop Pro or Photoshop ofcourse ;D
OK now a brief explanation about files, after downloading all the tools mentioned above ,try opening an already made addon, something simple like some soldiers, try do download one of the first ones being made check our addon depot for that, than use the DePbo or OFP_Decrypter 1.5 tool on the .pbo file, you'll notice it opened a new folder just beside the "addon".pbo file,
now open the folder and check the files there, you should have one or two .p3d files, a lot of .paa and .pac files and a .cpp file, here is what they are:
.p3d file = this is the model file, we'll leave this one for now.
.paa and .pac files = you remenber the tool called Textview? Try opening one of this files with it, and save them as .tga, than open it with Photoshop or Paintshop Pro.
.cpp file = well this is the file that tells the game what this addon is, example: Tank,Soldier,Plane,Armour,weapons, type of fire, place of the model, and so on, let's say this one is the brain of the addon
Ok now that you already know the basics, you should make some paintings or photographic manipulation ;D
Try changing one of the .paa or.pac files a bit in Photoshop or Paintshop Pro than overight the .tga file, and than with TextView save it again to .paa or .pac as it was before.
Next, overight the old file with the one you changed placing it inside the folder where it was before, now using the StuffPbo or MakePbo tool, save the folder with exactely the same name as it has before. Now you have the same .pbo file with the same name, but with your first edited texture replacing the old one ;D
Place this file inside your ofp\addons folder and go to the game. In the game go to the editor and choose the units you've changed you should know by the name they have, also read the readme file that comes with the addon it will tell you where you'll find them.
This is more or less what you'll need to know to have a basic knowlege of an addon, as obvious you'll neet to know much more, but that is what this forum is all about, just ask and you'll be anwsered no question is too stup**
I've been looking at the tutorials available, check this ones they will help
Commented CPP Files
Config.cpp commands
Config.cpp File Tutorial
Texturing Addons
for more questions just ask mate
and btw Welcome to Addon Making