That's a really broad kind of question. There's a summary of information about Certificate Transparency in the Let's Encrypt documentation, though it focuses on the logs that the Let's Encrypt organization runs:
And there's a web site with information about Certificate Transparency in general:
The actual mechanics of "looking" at the logs is a bit more complicated than what you might be expecting, though, as they're put together in a fancy cryptographic way to ensure that they aren't tampered with and that the logs are upholding their promises to include all certificates submitted to them. While it's possible to query the various logs oneself, there's a lot of data there and most end-users would take advantage of a "log aggregator" type service that gets the information from all the logs and presents it in an easier-to-search format so that one can look at, say, just the certificates for one's own domain across the various public logs. Here are the popular services that I know of:
- crt.sh by Sectigo
- Censys Certificates
- Facebook Transparency Monitoring (needs a Facebook account)
- Certstream
- Entrust Certificate Search