Trying to connect externally registered domains to have multiple sites hosted with WordPress

Hello,

I own a handful of domains registered on Domain.com. When creating my InMotion hosting account I selected one of those domains to be my primary domain, and because it's a registered domain, the site will work normally. What I'm struggling with is adding my other registered domains to my hosting plan. I was able to give my primary domain at Domain.com the InMotion nameservers (ns1.inmotionhosting.com, ns2.inmotionhosting.com) and it works fine, I installed WP and am making the site. My goal is to install and build WordPress sites with all of my domains registered on Domain.com but I'm doing something wrong.

To add a second domain I did the following steps:

1) In the InMotion Account Management Panel I selected the cPanel button beneath my primary domain hosting account.

2) In cPanel Tools I clicked Domains and Create A New Domain

3) I entered a domain that is already registered (on Domain.com) then unchecked the setting "Share document root" because it says that "If the document root is shared then the created domain will serve the same content as your primary domain" which I do not want.

4) I install WordPress on this new domain so that there is something to show once DNS is setup on Domain.com.

5) On Domain.com, for this particular domain I'm trying to give it the nameservers for InMotion but I don't know any others besides the ones I used for my primary domain (ns1.inmotionhosting.com, ns2.inmotionhosting.com). I put those into the nameservers for this domain and now both my primary and new domain will open the site for the primary domain.

To be clear about what I want:

DOMAIN.COM (what I have)

- domain_1

- domain_2

- domain_3

INMOTION (what I want hosted)

-domain_1 with WordPress Install

-domain_2 with WordPress Install

-domain_3 with WordPress Install

How can do I correctly point my domains I have registered on Domain.com to the domains I create on InMotion? My goal is to create and host WordPress sites for clients by buying the domain on Domain.com then using InMotion to host it and install WordPress.

I believe my plan is the Power Plan Web Hosting.