Further to what catacaustic mentions, you will change the nameservers for all three domains via your GD Domains manager to the values you see in your HG account:
http://support.godaddy.com/help/article/664/setting-nameservers-for-your-domain-names?pc_split_value=3
Use this option:
Setting Custom Nameservers for a Domain Name Registered with Us
Note, however, that this change is not immediately effective and can take upwards of 24 hours (or more) to be available to use; this is normal.
When you set up your HG account, you supplied one domain to be the primary domain for that account. To make life easier, especially for someone just starting out, I would suggest installing WP into the root of the hosting account.
I would also suggest, in your case, to use the QuickInstall option to install WP for all three domains. The thing to make note of with this method, is that the other two sites will be installed in sub folders in the root account. I generally create these ahead of time using the File Manager option in the HG cPanel.
To sum it up:
– change the nameservers at GD
– create two new folders in the root of your HG account, e.g. site2 and site3 (or whatever, just no spaces)
– use QuickInstall to install WP three times:
— first, to the root of the account (you will be presented a path suggestion of where to install; for the first, leave as-is
— for the second and third site, make SURE you add the folder name for each on in the space provided when asked where to install WP
— PLEASE note the credentials you use for each install and save them somewhere … you will be provided an email with them after the install as well as be shown them on the install completion screen 🙂
– use the Addon Domain option in the HG cPanel to set up the second and third domains to point to their respective folders.
Once that is all done (and the nameservers have become effective), you will access the three sites with:
http://www.primary_domain.com – public view
http://www.primary_domain.com/wp-admin – site log in
http://www.site1.com – public view
http://www.site1.com/wp-admin – site log in
http://www.site2.com – public view
http://www.site2.com/wp-admin – site log in
Repeat the steps for the second and third sites for any additional WP sites 🙂
Keep in mind, however, the the QuickInstall of WP from HG adds some additional plugins that are not part of the WP core:
– Jetpack
– Mojo Marketplace
– Sidekick
– WP Super Cache
I would suggest you deactivate at least WP Super Cache until the site is finished the initial stage of completion as changes may not be readily apparent from the public side, depending upon the plugin settings.
This is also a reason I prefer the manual install method; only the core gets installed and what is added later, I put there myself 🙂
Good luck! 🙂
