My account is registered with Godaddy. It is hosted on siteground.com. Here are my current configurations:

1) Godaddy Redirect Settings
Forwarding to: = www.knownogood.com
Redirect Type = 302 Moved Temporarily

2) Site Mananger (www.knownogood.com)
id = fassionate
Site Name = Fassionate
Domains = knownogood.com/multisites/fassionate
db server localhost
DB = knownogo_jo151
Prefix = jos2_
User = knownogo_fashion
status = Confirmed
***The slave site appears to be fine. I can log in.

3) CPanel Addon Settings
Addon Domains = fassionate.com
Document Root = /public_html/multisites/fassionate
Username = fassionate
Redirects to = not redirected
Actions = Remove Manage Redirection

***When I type fassionate.com in my browser it goes to knownogood.com. I want it to resolve to knownogood.com/multisites/fassionate

but I ONLY want to see fassionate.com for any link that I click. I should never see anything related to knownogood.com

Please help

Case 1)
You can NOT use redirect in GoDaddy but have to define a real sub-domain or domain and give a real path.
When you use a redirect, this mean that the original domain name is lost.

Case 2) As this is OK now, I suppose you have understood your problem.

Case 3) When I have tested, it seems that you have use the redirect because the URL is modified when it arrives and is replaced by www.knownogood.com/
The definition that you have given in this post, seems to be correct as you have not redirected and you have assign the directory of you current working slave.
You have to check in JMS that you have also the domain
fassionate.com and www.fassionate.com defined in your site manager (Case 2).
For the moment, you have put only one domain but you can specify all the domain you want.
In your case (case 2), I think you should have the list of domain
Domains = knownogood.com/multisites/fassionate ,
fassionate.com ,
www.fassionate.com

So remove www.knownogood.com/ from the settings in Godaddy?

Do I need to do anything with my Godaddy account (which is just the registrar)?

Thanks

I don't understand why you say remove www.knownogood.com/ that is your master website.
The problem was in the www.fassionate.com definition if I have well understood.

Remove from the configuration... Currently I have in my Godaddy account a redirection to www.knownogood.com/multisites/fassionate.

Should there be a redirection??? If not should there be anything in my Godaddy account other than the fact that I have fassionate.com registered with Godaddy?

In GoDaddy, I know that you can define a domain without the redirection.
To help you, see the FAQ www.jms2win.com/faq#sec-78 that show you how to configure GoDaddy. You will see that it does not use the redirection but specify the directory path where must be located the domain.
This is what you have to do.