Bombed Dream Job Interview, How do I stay in touch with the person high up who got me there?

Hi Reddit, Could really use your help! So I was contacted by a manager of a manger who works at my dream company on Linkedin. So hes pretty high up, and he wanted me to interview with them for a position (my dream job). I was ecstatic, but unfortunately, due to the lack of communication and miscommunication from friends who worked at said company, I thought my interview was actually a screening where I would learn more about the job, how much it paid, etc. Also this was actually my very first interview/screening for a real job, so I didn't know what to expect.

But it wasn't like that. So I bombed that interview Hard. I didn't get the job, and he let me know and hoped we could keep in touch. I messaged him back saying thanks for the the opportunity and such.

This was over a month ago. I still am very much wanting to work there and work at that job. I realize now that I don't have the exact experience they were looking for, and I very much want to keep in touch with him. How do I do that? I want to add him on Linkedin and establish a good connection. I still have so many regrets, but its great to realize that this is the direction I want to go towards.

Help please, Reddit?