At a technical level, renewal always means making a new certificate; there is no way in the certificate technology to extend the lifetime of an existing certificate.
However, some tools refer to a process of obtaining and installing a new certificate with identical coverage in place of the old one as “renewal” (for example, our Certbot tool uses that term). This is a pretty common term in the industry, but it always technically involves getting a fresh certificate.
Depending on what software you used to obtain the certificate, there might be a convenient feature to “renew” by obtaining a new one. However, if you used a web-based tool (it wouldn’t be the Let’s Encrypt web site itself, because there’s no web-based certificate issuance feature created by Let’s Encrypt itself; maybe ZeroSSL or gethttpsforfree?), there is probably no automated way to handle this and you’ll probably need to redo the same steps that you followed the first time.