Hi @Feather,
You can only install without their help if you have root access (not just shell access). I think this is never the case on HostGator. I guess the documentation has omitted to mention this important detail.
I have mentioned to people, most recently a few minutes ago in
that if you have to pay HostGator $10 every time you install a certificate, Let's Encrypt will actually be a money-losing option for you in comparison to buying a longer-lived certificate from another CA. HostGator policies make us not the most economical option for HostGator's customers.