What magazine is it? I am no expert, but I think you may need to get a lemmy account to find your magazine first, and then it will start federating.
When I was having trouble finding a Lemmy community from Kbin, I had to go to that lemmy community from Kbin where I got a 404 error. After that, I noticed the lemmy community started federating with Kbin. I am assuming the same is true in reverse.
Again, I am no expert so if someone has better information, please correct me!
livus