@sdbish, you should first double-check that there is somewhere that the web host allows you to install a certificate that you obtain from a certificate authority. If they don’t let you do this (or they charge money for the process that you’re not willing to pay), there is nothing that we can do about that because it’s simply a matter of hosting provider policy.
For example, there’s a rather popular host called HostGator that requires people to interact with their support to install certificates, and charges $10 each time for the process (making Let’s Encrypt a bad financial option for HostGator users because even though our certificates are totally free, the hosting provider’s install charges add up to more than the price of a longer-lived paid certificate from another certificate authority).
You should also consider that in a shared hosting environment like this, you will probably have to do something every time the certificate is going to expire in order to install a new one. With Let’s Encrypt, that’s every three months (and we recommend trying to renew the certificate every two months, in case anything goes wrong). If the
sudo command had worked, there would have been an option to automate this process entirely; since it didn’t, there probably isn’t.
If you’re OK with all of that, we can give you some options—the easiest might be the web site https://zerossl.com/, which gets Let’s Encrypt certificates for you inside your web browser.