I wan tto know a way to start it without the box disappearing in like a second and how I is meant to be launched
see Wiki - doPak (http://www.simutrans-germany.com/wiki/wiki/tiki-index.php?page=en_doPak&structure=en_Devel_Index&page_ref_id=463)
I don't understand the article I can't find anything specific. I am trying to be polite but maybe you will understand. I was going to move the PAK128 BRITAIN-Ex. Enviro 200 dual door and single to Simutrans standard PAK 128 Britain.
Although the article linked by Frank looks quite clear to me, here is another one (http://simutrans.fr/doku.php?id=en:tutomakeobj) which is written with a step-by-step approach. To sum it up, makeobj box disappears immediately because it is meant to be used in a command line (if you have windows, then run or search for the program called "cmd", it should give you a command line shell).
I can tell you from my experience that makeobj is never as simple as it seems. You will have to put in some effort to figure out how to get it running. And there may well be cryptic looking error messages that requires some figuring out and messing about.
If you're not comfortable with the command line in your OS, it's probably better to get familiar with that, first.
If you tell us what OS you're running, maybe we can point you to a tutorial on that.
Basically, we're a small community, so as long as you put in the effort, we'll try to help - probably. It just depends on if anyone has the energy to help. But we'll try. :)
I run Windows 10 32-bit
Here's a good place to start: http://www.computerhope.com/issues/chusedos.htm
Another good one: http://dosprompt.info/
On WIndows you can start a commandbox (aka dosbox):
While on the desktop, press the Windows logo key; hold it and press "R" to open the Run dialog box.
In the Run dialog box, type cmd and then press Enter.
The commandbox opens as a new (probably black) window.
In that new windows change to the folder where makeobj.exe is at the commandprompt (just type it):
cd \"replace this with path to folder where makeobj.exe is"
To start makeobj just type makeobj at the commandprompt. It will give you some help with makeobj.exe itself.
On windows 8 and 10 you can also open the commandline by right-clicking the start menu Windows logo or by hitting Win+X.
Two options for Command Prompt are there, one is for running as admin, which is not necessary for makeobj.