Just need advice

Hey, so I am 14 years old, and my grandma, um, well, granddad has just come out as trans gender. I am a firm believer in being your self, and have no issue with any LGBT+ people, however, I am finding this a little hard to process. In no way am I trying to offend anyone, and I just want my nana (I’m not sure what to call them) to be happy. If any of you have some advice on how to (for want of a better word) deal with this situation, it would be greatly appreciated. I’m just confused, and need to know what I have to do differently.