There was a book called "The Venona Secrets", available on Amazon. It's not the only source - it's all over the internet. Googling McCarthy Venona yields plenty of material.
I’ll order the book. In the meantime I googled McCarthy and Venona and couldn’t find anything suggesting that he had access to the transcripts, beyond one person In a blog post speculating that it would make sense. I’ve read a couple books on McCarthy published long after the transcripts became public. Plenty of people write about the transcripts vindicating McCarthy but I haven’t see any evidence produced that he had access to them. There’s also an anti-McCarthy article on frontpage that argues he couldn’t have access because so few of the relevant names match his own lists. But I didn’t find that convincing either.