Site5 told me to get code from Let’s Encrypt and Site5 would install it and that we will have to do this every 3 months on each of my hosting accounts. I am a reseller and this is just one of the websites that wants SSL. Who do I request this code from?
that's not the idea of using Letsencrypt certificates.
Please start with some basics.
If you don't have root access, your options are limited. Perhaps it's better if you switch to a hoster with integrated Letsencrypt support. Or to a server with root access.
Yes, I know that. Thank you, but this is what I have and to move many many websites now is more difficult. Site5 is willing to install if I get code for each - only my non-profit customers need the free SSL and that is not the bulk of my customers, the others pay Site5’s fee for auto SSL. I want to help them all I can.
If you want an experience akin to a paid CA’s certificate issuance flow, except without the payment part and with a more frequent renewal obligation, you could use ZeroSSL (which is a third-party web interface to Let’s Encrypt certificate issuance). As other people have suggested, this isn’t a recommended way to use Let’s Encrypt from the point of view of Let’s Encrypt’s developers, because Let’s Encrypt is designed to be used with automated renewals rather than manual renewals.