Site not showing on domain

I’ve recently downloaded and installed the new
WP into my Hostgator account.
Whenever I type the domain into my laptop browser,
I see the Hostgator log in screen.
But, whenever I type the domain into my phone, I see
my WP site.

I was told that I may be missing an index.html file,
but I’m unable to locate it in my computer.

What is it I should do?

Thanks!