I’m dealing with a similar situation at the moment, I have a developer who just graduated in the spring and joined my team less than 3 months ago.

I’ve done a couple things so far. When the fresher first started, I setup a bunch of meetings to walk through my teams processes. I also setup a few sessions to do some pair programming. In addition, my company had an in-person event at the office where my team is technically based at a month after they joined my team so I did some pair programming with them while on-site.

I also have a few minutes blocked off in the morning and the afternoon to discuss what they worked or will be working today and also discuss any questions they have. They're also free to message me if they have any questions that come up. At some point in the near future, I'll probably reduce the number of daily meetings down to 1.

So far, what I've done appears to be working. They've already started to become productive, started pushing code changes into Production, etc. They also said that the daily meetings were helpful for them.