You should really be taking the initiative and asking for the repo, asking for and learning the whole tech stack, reading the documentation in the time and looking around in the channels.

There's usually multiple programming languages, multiple frameworks, one cloud provider, a number of cloud services that you have to learn, the CI/CD pipeline and the languages used in the CI/CD pipeline.

The senior developers will use many programming language features that you are unfamiliar with that make it difficult to figure out what is going on in the code, so any free time should be used grinding your understanding up on the codebase because once the tickets start you will find it difficult to catch up, unless you already know the various language elements and any tricky stuff well.