[Todo]

Where do I have to extract / install the mission files to make them work properly?

I mean the files in the Mission Downloads and the Unofficial Download pages. There's also a Campaign section and a Stand-alone section. Do I have to extract / install the Campaign files to a different directory and the Stand-alone files into another?

Some readmes say they need to be put in X\TBP\Missons -folder (that doesn't exist) and others say they have to be put in the X\TBP\ -folder.

EDIT: Corrected a few spelling errors and made the question a bit more understandable.

[Cavane]

X\TBP\data\missions is the folder you're looking for.  Also, most downloads will come with a readme telling you how to properly install the files.

[karajorma]

The fact is that either of those two will work but putting things in Data\Missions (you'll have to create it manually) is much tidier and is also where everyone else expects you to have them

[0rph3u5]

the folder will also come once you created your frist own mission or the thing that looks like one... Fred should do that for you