How to Add more text fields?

How do I customize my newthread.php to add in new text fields. Ex. in my case instead of message I need $tab, $explanation, and $key as well as username, forum id etc. I would also like to make a form that posted a thread on a different html document. I think I have already done that correctly.

Seperate html document:
<form METHOD="POST" NAME="postthread" action="http://www.guitar-rampage.f2s.com/Lessons/Contribute/upload/newthread.php?action=postthread">
<table width="100%">
<tr><td valign=top>
Your Name:
</td><td valign=top>
<input type=text name="username" value="" size="40">
</td>
</tr>

<tr><td valign=top>
<p> </p>
Subject:
</td><td valign=top>
<p> </p>
<input type=text name="subject" value="" size="40">
<p> </p>
</td>
</tr>

<tr><td valign=top>
Explanation 1:
<p><font color=blue>HTML OK in here. Type &lt;p&gt; to separate paragraphs.
</td><td valign=top>
<TEXTAREA NAME="explanation" value="" ROWS=10 COLS=82 wrap=physical>

</textarea>
</td></tr>
<tr>
<td valign=top>
Key:
</td><td valign=top>
<input type=text name="key" value="" size="20">
</td></tr>
<tr><td valign=top>
Tab:
<p><font color=blue>
Don't put explanation text under the tab!
</td><td valign=top>
<TEXTAREA NAME="tab" ROWS=15 COLS=82 wrap=physical>

E |-------------------------------|----------------------------------|
B |-------------------------------|----------------------------------|
G |-------------------------------|----------------------------------|
D |-------------------------------|----------------------------------|
A |-------------------------------|----------------------------------|
E |-------------------------------|----------------------------------|

E |-------------------------------|----------------------------------|
B |-------------------------------|----------------------------------|
G |-------------------------------|----------------------------------|
D |-------------------------------|----------------------------------|
A |-------------------------------|----------------------------------|
E |-------------------------------|----------------------------------|

</textarea>
</td></tr>
<tr><th colspan=2 align=left>

<p> </p>
Categorization: If you don't fill these out, no one can find your work.
<p>
</th>
</tr>
<tr><td valign=top>
Category:
</td><td valign=top>
<select name="forumid">
<option value="1">Playing
<option value="2">Purchasing
<option value="3">Recording
<option value="4">Other

</select>
</td></tr>

</td>
</tr>

</td></tr>
<tr><td valign=top>
<p> </p>
<table bgcolor=blue><tr><td>
<INPUT TYPE="HIDDEN" NAME="action" VALUE="postthread">
<INPUT TYPE="SUBMIT" NAME="submit" VALUE="Submit New Lesson">
<INPUT TYPE="RESET" NAME="Reset" VALUE="Clear Fields">
</td></tr></table>
</form>
</tr></td>
<tr><td valign=top>
<table bgcolor=red><tr><td valign=top>
<form>
<input type=button value=" Cancel " onclick="history.go(-1);">
</form>
-----------------------------------------------------------

[Mike Sullivan]

You may not post full files. I've had to edit out newthread.php 3 times now.

This isn't a stock vB question so moving to hacking.