Go to your game files, then GameData\Data\_LVL_PC
Un zip your Star fire mod to the desktop (or any were you like, It is just easier to find stuff on the desktop) Open the "Star fire mod 1" folder and copy the file called "core" into the the directory above, say yes to replace the file. Do the same with the "mission" file.
In the same directory, open a folder called "SIDE".
Then inside the "Star fire mod 1" folder you will see a folder called "The sfsm units" open it and select all the files and copy them into the "SIDE" folder say yes to replace the files.
In the _LVL_PC folder, open a folder called "FPM".
Then inside the "Star fire mod 1" folder you will see a folder called "The arms and the cabs" open it and you will see folders Select them and copy them into the "FPM" folder.
In _LVL_PC again,
You will see a folder called TAT and in the "Star fire mod 1" folder open the folder called "vehmaps" inside there will be file called tat1.
Tat1 goes inside the folder TAT
Kas2 and Kas1 goes into the KAS folder
You get the idea The first part of the name of the files is the folder they go in.
Say yes to overwrite.
You are all done.