Custom fields in new thread

[zmmmzz]

I'd like to add a custom field to new threads.
So far I have this.

I execute this SQL Query:

ALTER TABLE table ADD (
         var VARCHAR(10) not null default ''
)

Table is the name of the vb thread table and var is the name of the field I'm adding.
In the template I add this:

 <div style="padding:$stylevar[formspacer]px">
<div>
<input type="text" class="bginput" size="10" name="var" value="" id="var" tabindex="1" /> $vbphrase[var_name]</div>

I add 3 new plugins:

newpost_process

if ($type == 'thread')
{
    $dataman->setr('var', $post['var']);
}

newthread_post_start

$vbulletin->input->clean_array_gpc('p', array('var' => TYPE_STR));

$newpost['var'] =& $vbulletin->GPC['var'];

threadfpdata_start

$this->validfields['var'] = array(TYPE_STR, REQ_NO);

I got this info from a vb.org article. Now I want to display the variable in postbit or showthread.
I think I need to add a new plugin to global_start but I'm not sure. How do I call it?