How can I access the certificate transparency logs?

The CT endpoints are correct, however you need to access it with the correct paths and parameters instead of the root endpoint.

For example, to access the STH (signed tree head), you use the URL: https://ct.googleapis.com/pilot/ct/v1/get-sth

Or to access log entries numbered 1000 to 1100: https://ct.googleapis.com/rocketeer/ct/v1/get-entries?start=1000&end=1100

RFC 6962 describes all the paths and parameters used for CT operations, or you can use a library like https://github.com/google/certificate-transparency.

Is this what you're looking for?

Google Transparency Report

It gives you the ability to search the CT logs for all certs issued to a particular domain.

If you do interested in programmatic accessing CT logs then one possible way forward could be the lib I made CTjs. There you could find an an example how to use it - it is example using all possible APIs and features of CT log. Also there is RFC6962 example on a real data from all known CT logs.