Here is a tutorial for using a mod-folder.
First of all: Many readme's say: "Put the pbo in your Flashpoint/addons folder"
or "Put the pbo in your Flashpoint/res/addons folder"
DON'T DO IT !
The more addons you have in your folders the higher the risk that 2 of them are not compatible to each other and cause errors in the game.
Best way is to assort your addons in different addon-folders (so called Mod folders).
The following picture shows my @KF_server modfolder:
To activate the addons within this folder you need a modified link to your OFP.exe
Mine looks like this:
F:\OperationFlashpoint\FLASHPOINTRESISTANCE.EXE -nomap -nosplash -mod=@KF_server
("-nomap" helps many different addons to save memory capacity,
"-nosplash lets you start OFP without the startup-screens (saves time),
"-mod=" activates the mod-folder... type the name of the modfolder after the "=". if you want to use more than one mod, seperate them with a semicolon:
e.g.: -mod=@ecp;llauma2;@KF_server
The PBOs in your modfolder must always be in a subfolder called "addons" (view the adress-line in the picture above) )
Though I told you, not to put addons in your standard-addons-folder, there are a few that became essential, because many mods or missions use them. To save diskspace I put them in my standard-ofp-addonsfolder, and I know these don't cause errors.
Here's a pic of my standard ofp addons folder (I marked the addons that do not belong to original ofp):
If you downloaded the KF_serverpack 1.4 you'll see that there are some addons I do not have in the @KF_server-folder but in my ofp/addons-folder. Do as you please, but you need them for playing KF Missions like "Nogova Crimes".
Just to have a reference, which addons are original and which are not, here is my res/addons-folder (I have no additional addon in there.):
Tutorial by Dr.Pepper