I assume that you know the TTools step... which you can find here in the tutorial section

You need the following steps to prepare the 3 textfiles for the TTools step. This is the way i usually do it...
1: Depending on texture package (limited or complete) add the textures to the aircraft. There's a txt file with all the necessary sections included
2: copy ALL the cfg sections to aircraft.txt, but dont overwrite the existing lines yet
3: Rebuild aircraft.txt, put the correct speeds for the correct aircraft type and renumber the lot
4: sort out the reg numbers in flightplans.txt. If the aircrafts.txt entry doesnt have a reg number its the most common variation. Usually the 'full' texture package covers all possible regs.
5: Compile the lot and copy to where you need it
6: Start FS
7: Go to one of the following airports: UUEE, UUWW, UUDD, USSS, UNNT, ULLI and watch the results