Custom Attachment Field in NewPost and Display as Preview next to thread in Forum

[asdfadrian]

I currently have made custom modified ForumDisplay.php and newthread.php

What I am asking how do I include a separate "Browse from computer" attachment input field into my newthread.php when a user is creating a thread like in the image below?

Here is my current Newthread.php. Boxed is the area I want to edit.


In place for the red box in the image displayed above I want to replace with the red box (the <Input> Fields with the Browse button) in the image below


Secondly how can I use the image in the custom attachment attached and display that as the image preview next to the forum thread title when browsing a forum? I want to achieve something that looks like this: