I have been making a custom home page for my site and I made a login form but I want to be able to use the mybb login on it. How would I go about getting this to work, I want to be able to have member login on the custom home page if they want
Interesting idea. I'm gonna look into this, sounds good.
You could edit the login template? or following the tutorial that tells you how to integrate your site with a login form.
<form action="member.php" method="post">
<input type="text" name="username" value="" />
<input type="password" name="password" value="" />
<input type="submit" name="submit" value="Login" />
<input type="hidden" name="action" value="do_login" />
</form>
This is a simple form which makes you able to login to your forum. You need to change action value of the form with your forum's member.php's path.