I usually find a tree or post to lean / lock my bike at night. I have seen two or more bikes leaning on each other for support. There is a trick I have seen where you loop a cord around your top tube and guy them to two tent stakes. You might want to put something between the cord and your bike to protect the finish. Otherwise, many bikes just lay on the ground. Expect dew on your bike in the morning.
I’m sure you will find your first time a true adventure. I wish you the best experience, and the wind always at your back.