Just put the saddle on your bike, adjust for the best fit & ride it a lot. The break in time varies. One of mine only took about 300 miles & it was comfortable out of the box, but I have a green Champion Special that has done over 3000 miles. It is better than when new but still needs more break in. I discussed this with my LBS owner & he has one with 5,000 miles that still isn't where he wants it, so be patient.
I agree with those who warn against to much proofide or neets foot oil. I picked up a new B17 for $10 at a swap meet that got to much of something & had badly sagged. Even after adjusting tension & with the sides laced together, it was only fit for short rides & not comfortable at all after 30-40 minutes. Don