You can set it up through a domain or subdomain. 

Install phpmyadmin:

apt-get install phpmyadmin

When it asks you what your web server is, choose neither of the given options and continue. 

Setup a new domain or subdomain and set the document root to:

DocumentRoot "/usr/share/phpmyadmin" 

That domain/subdomain should then take you to phpmyadmin.

If you have any questions, I can try to help you out. 

Feel free to message me on discord: ImJT#8937

Ignas

I am unable to set my hostname from within TinyCP as well. The support, from the community and developer, are fairly poor from what I have noticed. I have been using TinyCP for around 2 months now and it's not bad; however, it is missing some functionally that I would very much miss from other panels. I am thinking about moving away from it and using something like VestaCP again.