oky here we go ...
Code:
#include <acknex.h>

STRING* WordText = "#4000"; //string with space for 4000chars (4000chars is the max length of file_str_read())
STRING* fileString = "test.txt"; //the file
var lineToRead = 3; //the line that should be read

TEXT* Word =
{
  layer = 15;
  pos_x = 100;
  pos_y = 100;
  font = "Verdana#15"; //here you forgot a font
  strings = 1;
  flags = SHADOW | OUTLINE | TRANSLUCENT | SHOW;
  alpha = 100;
} 

void main() {
	
	video_mode = 8;
	video_screen = 2;
	
	var myFile = file_open_read(fileString); //you have to use file_open_READ to read the file
	if(myFile == 0) error("Couldn't open the file!");
	
	var i;
	for(i=0;i<lineToRead;i++) {
		file_str_read(myFile,WordText);
	}
	
	file_close(myFile);
	str_cpy((Word.pstring)[0], WordText);
}