You can register your domain name with the letter "Ñ", but not before knowing some peculiarities about this decision.
The domain with Ñ will not work with Google Analytics. In order to use it, you will have to convert it to PunyCode format to include it in Google Analytics.
Configuration of the email client . Depending on the email client you use, you may need to set the domain in PunyCode format (see below how to convert it to this format).
PunyCode is an encoding syntax used in programming that allows, so to speak, to convert certain specific characters (such as the "Ñ") to a format understandable by all computer languages.
It is possible that once you have registered the domain with "ñ", when you access your Cloud, you see the name written differently, it is still a "Ñ", but what you see is the name in PunyCode format.
To register a domain with "Ñ" in SW Hosting, it is done in the same way as with any other domain. Click on the link to register it, Register domain
For SEO positioning the "Ñ" is recommended, Google searches with both "N" and "Ñ", although if the match is exact, it will position you a little better in the results.