There are two routes, the key differentiator is are the resulting name hierarchy public (like .com) or is it yours and jealously to be guarded from all others (like .mil) ?
If the former ICANN will also require you to do a bunch of legal work to ensure that when you fail (because realistically you will) any names can be scooped up and preserved by a new operator of the TLD.
If the latter you're likely to have a tougher time defending why you should own this, unless you're a huge global brand.
Then you need to either spend a lot of money (again estimate $1M a year at least at first) yourself on infrastructure to serve your TLD, or you need to pay somebody else with relevant experience to do it for you.
A surprising number of companies bought vanity TLDs which they then don't use at all because of course they're much less convenient than a short name in an existing TLD. For example the KerryProperties TLD isn't used at all, kerryprops.com is much easier.
Why so much money?
https://en.wikipedia.org/wiki/List_of_Internet_top-level_dom...
I wish there was something up at https://google.google or https://apple.apple
$ whois goog
% IANA WHOIS server
% for more information on IANA, visit http://www.iana.org
% This query returned 1 object
domain: GOOG
organisation: Charleston Road Registry Inc.
address: 1600 Amphitheatre Parkway Mountain View, CA 94043 US
address: United States
contact: administrative
name: Domains Policy and Compliance
organisation: Google Inc
address: 601 N. 34th Street
address: Seattle, WA 98103
address: United States
phone: 1 202 642 2325
fax-no: 1 650 492 5631
e-mail: [email protected]Sadly it always defaults to the first logged in user, which makes it almost entirely useless to me.