Add another domain to an existing Exchange Server 2016 server on MS Server 2013R2

Hello I am looking for opinions on the best method to add another domain to a existing Exchange server 2016 system (installed on server 2012R2) for another company for email.  This is a complete stand alone server running all the usual items installed by the default Exchange 2016 installation process. Originally the first domain was abc.net as the .com was taken, I added the abc.com later but the DNS and AD were setup with the abc.net and that is what the server is using.  We have started another company xyz.com and want to add that domain to our existing exchange server 2016 tor emails for that company. What would be the best steps to take on this server to add this new xyz.com domain and used it for our new company with phones, outlook, and OWA access?
Thanks, Bill