Welcome to the forum.

Now to the humidor.

After it is seasoned some the wood slightly expands and the seal will get better.
I have a Yukon thats basically the same as the one you got and it didn't seem to seal up very well when i first got it but now its fine.

I use the small humidor to keep pipe tobacco samplers in now so im not real concerned if it stays at a perfect humidity, But back when i used it for cigars it was no problem after a few weeks of using it.