BOUGHT A DOMAIN AT NAMECHEAP. NOW WHAT?

Make a porn site.

Get a Tuta account and direct your emails there, here's a how to: https://www.youtube.com/watch?v=NKYyqRtRc0o

Tuta has unlimited alias email addresses for your domain, pretty neat.

You will need an email hosting service or host your own mail server (really not recommended). There is a free service called Zoho Mail, that's what I use. If you want more control and more options you can buy Microsoft 365 with Outlook which is 5-7$ per user, or Google Workspace which also costs about the same, or Zoho also offers more premium plans. For self hosting you would go with a Microsoft Exchange server but honestly it's extremely hard, and the server license is expensive. You need to have an actual physical server and stuff like that, so just use a service like the ones I mentioned above. That's about it. Good luck setting it up!

Edit : Zoho offers very good documentation and is extremely easy to setup. Just lookup Zoho Mail. For Microsoft 365 and Outlook you will have to use the M365 Admin Center and also configure stuff in Azure Active Directory, so quite a lot of stuff, so basically Microsoft 365 is quite more difficult to install for a non-technical user like you. I would suggest hiring someone to do it for you if you don't wanna go the easy route.

Get skiff mail free and more refine than zoho

NOW MAKE ALLCAPS POSTS ON REDDIT AND PROFIT

Domain does not equal email...

You also need an email server and they should tell you how to set up the MX records for your domain. As you are using Namecheap, you will find it easy to use their email service at https://www.namecheap.com/hosting/email/

Using Outlook as the mail server for your domain is possible BUT it depends on your MS contract and some, e.g. 365 Personal have changes coming up at the end of this month - start at https://support.microsoft.com/en-us/office/get-a-personalized-email-address-in-microsoft-365-75416a58-b225-4c02-8c07-8979403b427b

You used to be able to use Outlook on the web to pull from SMTP or IMAP servers so you had everything in one inbox but I honestly do not know if that exists now and still requires the external email server.

First, figure out that caps lock

I would repair my capslock next :)