This would require forethoughts as to what you want to add, where (which nation) you want to add the building to and how (availability of unit, upgrade levels, etc.). There is an additional step that you will need to do also. Because you will be introducing new files, you must remember that new MD files must be listed in NMLIST.TXT file and its description given in TEXT\MDLIST.TXT file. Now you go to the nation NDS file that you wish to add this new unit to and start editing. You must decide what its name is going to be, where it will be born and what position will it be placed in the family plus its potential role when it matures. So you go through the process of adding this new member with a new name in the [MEMBERS] entry. Then you must decided where it is going to be produced at under the [FIXED_PRODUCE] entry. After this, you must decide on whether or not its going to be available by default under [ENABLED] entry, etc. You then must go through the whole NDS file entries to complete the addition of this new member.
List of files that you need to get a new barrack working for example:
I took the AUCEN.MD from the Imperia mod to test with.
Take the AuCen.GP & AuCen2.GP( extract from Imperia, its under the various mod & patch files)
Let’s use an already existing icon to make things easier. ( Sklad)(Storehouse icon)&( change it in the .md file)
Make or copy a DESCRIPTION+AUCEN.MD and add its description
Add the entry to the NMLIST.TXT
Add the entry to the TEXT+MDLIST.TXT
Add the entry to the FILELIST.LST ( MASM)
Add the entry to the AUSTRIA.NDS under [MEMBERS] [FIXED PRODUCE] [ENABLE]
Run dmcr.exe, find your newly Austrian center or barrack whatever you wanna make of it.
I had an error first time I ran this, I forgot to change in the AUCEN.MD file the userlc from UNITSGP\AuCen to AuCen. (Just delete the UNITSGP\ ).
For making troops and upgrades in the building I refer to the .nds file information in the other modding sections
-Change the name of the md file.
-Then inside the md file, change the NAME entry
-Then add the new name to nmlist.txt
-Then make the entry in mdlist.txt ( this is the name of the md in capitals)+ a description to show up in game
-Then add the entry in the nds file under [MEMBERS] [FIXED PRODUCE] [ENABLED] [COUNTRY] and possibly more depending on what you want to do with the unit.