Hello @Yogesh,
Placing the server on a particular domain address is a little outside of the scope of Alteryx itself, but hopefully the following information will help!
In order to direct a particular domain address (let's assume we want gallery.yourcompanydomain.com) to your Gallery, you would need to have a proper DNS (Domain Name System) record, typically referred to as an "A Record" added to point to your server's IP address. This would tell client machines, when looking up the information for your domain, that gallery.yourcompanydomain.com should send the request to your Alteryx Server's IP address. If you would like more information about how DNS works, I located a great article here:
https://www.cloudflare.com/learning/dns/what-is-dns/
In most corporate environments, DNS for the company's official website address(es) is/are typically handled by an IT team, in which case you would need to work with your IT team to have a particular address assigned to your server machine to use for your Gallery. The proper contact could vary greatly by organization, but your IT team is normally a good starting point of contact if you're not sure who to ask.
Regarding the question on SSL, once your DNS entry is setup as above, a proper SSL certificate will need to be created and installed on the server in order for client machines to trust the connection to your Gallery server (otherwise they'll receive those "this website is insecure" and other similar warnings). As with the DNS records, most SSL certificates that need to be issued inside an organization are also provided by an IT group. There are also third party services that can issue an SSL certificate for a particular domain, but you should definitely check with your IT team first!
The SSL certificate would need to be issued so that it encompasses the domain that was setup for your Alteryx Server, so either something like a wildcard (*.yourcompanydomain.com) or the exact sub-domain (gallery.yourcompanydomain.com) would likely be setup in the SSL certificate. This certificate would also need to be trusted by the clients that will be visiting your Gallery. Most companies have a particular Certificate Authority that signs their certificates (they may even sign and trust their own certificates) so that they are already trusted by all the machines they use. A self-signed certificate would very likely not be trusted in these environments, as other client machines where the certificate isn't installed in the trust storage won't trust the entity (yourself or whomever generated the certificate) that signed the certificate originally.
This is kind of a basic overview, but once you have both of these items and have installed the certificate on your server correctly (following the article you linked above - make sure it has a private key attached for your server to encrypt your traffic!), binding it to the server's SSL port and setting the base Gallery URL to use the domain specified in the DNS record and the SSL certificate, your clients should then be able to connect to the server with SSL on your brand new Gallery URL.
If you have any trouble once you've obtained the above items, such as the Gallery not starting properly after installing your SSL certificate, I might recommend reaching out to our support group directly so we can help make sure things are configured properly!
Mike Spoula
Senior Solutions Architect
Alteryx
