Written By: Ebola
Info: 3 Ways of adding the FS lump to your map.

This is very easy.

1.
Use lvlinfo.exe:
command line usage: lvlinfo.exe myscript.txt mywad.wad

2.
Use Wintex.

Load the level wad in wintex, then select the "Mapxx" lump and replace it with your script lump, using "load entry from file" in the "Edit" menu.

3.
Use DeepSea.

DeePsea directly "imports" a text file into any level name.
Press F7 and "Save Lump File to Current Level".