I want to set up a vault on my Mac and transfer it to the Android (and vice versa if I need)

Can someone please assist (I’ve spent 2 hours trying to figure out something I would have thought was simple)?

I want to set up a vault on my Mac and transfer it over to my Android phone to access. I simply cannot work out how to do it and be able to access the files. I can see the vault but there is no masterkey associated with it and I cannot click on the vault name in order to open it.

Thanks for your help.