Speaking from past experience it can be quite a nerve wrecking thought to introduce your partner into kitten play, due to there being such a wide variety of aspects to grasp an understanding on and it still being a rather unheard of lifestyle makes it exasperating to discover reliable and detailed information. Additionally, there is the possibility of being judged for something that makes you happy, but if the person you are with truly cares for you then they'll listen with an open mind before coming to any conclusion on this lifestyle.
Since kitten play requires a deep understanding of the mindset and what is involved it can be overwhelming when the information is thrown onto you, for this reason I made it into a game for my partner to gain knowledge on this way of life. Instead of simply saying what it was all at once I separated it into categories and each week I'd let him choose a category then explain it to him in the best of my ability. For example, there was a rules category which also linked into rewards and punishments, and this covered the various basic rules which most pets follow along with types of rewards that can be given if the pet has done well. On the other hand, we also discussed the punishments that can be done whether they be sexual or non-sexual should be agreed upon by all parties involved in the relationship.
Personally, I believe this way of presenting kitten play makes it a smoother graduation into a deeper understanding for your partner without frightening them away. I find even now after explaining all the categories my partner is still learning and likewise so am I, but we both have an open mind and a keen interest into kitten play whether it be me as a submissive kitten or him as a dominant Master/Owner.
I wish good luck to all of you how are planning to open up to your partner, I can promise you it's a weight off your chest for no longer having to keep a secret. I hope this helped my lovelies