First threesome advice

Hi guys I am posting this in multiple groups to try to maximize responses. Sorry if you end up seeing it twice!

So my husband and I are about to be married for two years. He's in his mid thirties, I'm in my early 20s. We are having our first threesome ever this saturday with a girl we met on tinder who is the same age as me (yes she's real, clean, and protected).

This is my first threesome ever and my first time ever with a girl but honestly I have wanted this for so long!! My husband and I already discussed all our boundaries, intentions, etc. But I am just still nervous! Nervous about what to do, how it will feel, how I will feel after, etc...

Anybody have any advice at all????

***please no comments saying we shouldn't do this or shaming me for our decision. Everyone experiences love and pleasure differently***

Thanks everyone!