It's easy to make a small mistake when you're creating a lot of inventory, for instance, you may forget to change the inventory type from Device to Container if you're creating a set.
If that's the case and you've accidentally created your Container as a Device, here's what you should do.
First, remove the mistake.
1. Locate the inventory created by accident and deactivate it manually or using a stock adjustment event.
2. Now navigate to the catalog and search for the incorrect catalog record.
3. Open up its detail screen and click "deactivate", this will prevent the catalog record from being used further. 
Next, create the container.
1. You'll need to create a new catalog # for the container, since you already used it in the prior catalog record.
This is because every Container must have a unique Catalog # and you already used the prior one.
Consider easy changes to modify the catalog #. For instance given the used Catalog number: 001, I could use: "#001", "Set 001", "001-1", etc.
2. Create the new container making sure to change the inventory type to "Container".