You need to specify what point of the texture corresponds to each vertex (where 0 represents the left or top and 1 represents the right or bottom).
Try something like:
glBegin(GL_QUADS);
{
GL11.glTexCoord2f(0, 0);
GL11.glVertex2f(x, y);
GL11.glTexCoord2f(1, 0);
GL11.glVertex2f(width + x, y);
GL11.glTexCoord2f(1, 1);
GL11.glVertex2f(width + x, height + y);
GL11.glTexCoord2f(0, 1);
GL11.glVertex2f(x, height + y);
}
You might have to flip the Y-values because of the way OpenGL's coordinates work (i.e. (0,0) is normally bottom-left instead of top-left).