The Wiccan Wonders Answer:
It would depend. I strongly suggest that you don’t open up the conversation but rather allow them to come to you with any questions or prejudices. They will not appreciate it if you try to force anything onto them. If they don’t want to hear your side, then you agree to disagree and move on.
That being said, if they are open and are just asking for an explanation, I usually start out with the rule of threefold and the wiccan rede. These are the easiest things to explain and there are definitely some parallels within Christianity. (Note, to some this sounds like “oh, so you can just do whatever you want.” I like to challenge these people to go through an entire week with the object of not harming anyone, including themselves. Remind them to consider all possible consequences to their actions as most harm is unintentional)
From there, you can cover the duality of the deities, your own personal beliefs, the fact that there is so much variety in how people follow Wicca, you can cover covens and circles (I generally parallel these to a church as a “safe space” of sorts), solitary practices. I would also touch on life after death, you can compare Summerland/heaven if you so choose.
Discuss whatever you love the best about Wicca, ask that they share their favourite parts of Christianity with you, compare and contrast. Make it into a conversation not just you spouting off your beliefs :)
In the end, Christianity sprouted out of Pagan religions, there are a lot of things in common, and there are some things that you probably won’t agree on. All of that is okay, just be respectful and have fun with it. You never know what you can learn or how you can rub off on someone else by approaching things in an open minded manner. :)
Good luck!! :)