I guess the sync to your cloud provider has finished?
Which provider do you use? If iCloud, then you have to store your vault inside a folder called „Cryptomator“.
You can test it. Just create a vault with your iPhone. After that check out your iCloud. Now you see your new vault inside the Cryptomator folder. (There’s also a file created with explanations.
Place/move your vault that you have created with windows in the Cryptomator folder in iCloud. . Now you can ad the vault to your Cryptomator app on the iPhone.