Once I dropped it in 20 consecutive answers in the source box. After that the domain got a softban, meaning I got a 999 error each time I tried to use it as a source. After I don't know how many days the softblock was removed and I was able to put the link in the source box again.
Realistically you can drop it in every answer you make, but I would spread the time frame of the creation of the answers. the answers I made were all well researched and accurate, the only reason I got that softban, I think is because I made 20 in 30-60 minutes.
So you can mask your link with a shortener, which is still allowed on YA, or you can spread your answers if you are answering straight with your domain.