Just paste this code i took from these forums, and modify it where you like, and put it on the page you want to add the login thingy to,
<form action="http://www.yoursite.com/forum/index.php?board=;action=login" method="POST">
<table border="0" width="400" cellspacing="1" cellpadding="0" bgcolor="#6394BD" class="bordercolor" align="center">
<tr>
<td class="windowbg" bgcolor="#AFC6DB" width="100%">
<table width="100%" cellspacing="0" cellpadding="3">
<tr>
<td class="titlebg" bgcolor="#6E94B7" colspan="2">
<img src="http://www.yabb.info/community/YaBBImages/login_sm.gif" alt="">
<font size=2 class="text1" color="#FFFFFF"><b>Login</b></font></td>
</tr><tr>
<td align="right" class="windowbg" bgcolor="#AFC6DB"><font size=2><b>Username:</b></font></td>
<td class="windowbg" bgcolor="#AFC6DB"><font size=2><input type=text name="user" size=20></font></td>
</tr><tr>
<td align="right" class="windowbg" bgcolor="#AFC6DB"><font size=2><b>Password:</b></font></td>
<td class="windowbg" bgcolor="#AFC6DB"><font size=2><input type=password name="passwrd" size=20></font></td>
</tr><tr>
<td align="right" class="windowbg" bgcolor="#AFC6DB"><font size=2><b>Session Length in Minutes:</b></font></td>
<td class="windowbg" bgcolor="#AFC6DB"><font size=2><input type=text name="cookielength" size=4 maxlength="4" value="60"></font></td>
</tr><tr>
<td align="right" class="windowbg" bgcolor="#AFC6DB"><font size=2><b>Always stay logged in:</b></font></td>
<td class="windowbg" bgcolor="#AFC6DB"><font size=2><input type=checkbox name="cookieneverexp"></font></td>
</tr><tr>
<td align=center colspan=2 class="windowbg" bgcolor="#AFC6DB"><BR><input type=submit value="Login">
</form>