Refitting EMU bodyshell

Hi All.   I know that this question has been asked, and, answered before. Hornby bodyshells have those silly plastic bits that every time I go near them they break. Bachmann are different they have screws which should be better, if one doesn’t lose them. Now for the question, I have the bodyshell off, of both of them, now I have to put back together, how do I do it? Happy New Year Kevin