If you are not ungated, then you will not be able to add an item to you inventory, create a shipping plan, or create shipping labels. You must be ungated before that can happen.
You have a few options. You can communicate with your supplier that you are working to get ungated, purchase the units, wait until you're approved, then have them ship to Amazon once you're approved and you can list.
If they have to ship right away, then you can have them just ship the products themselves to you, or to a nearby prep center using whatever shipping they want to use. Then once you're approved, you or the prep center can ship to Amazon.
Here is a link which helps to go over some options: https://algo-online-retail.tribe.so/question/getting-ungated-in-a-brand-is-a-bit-circular-in-that-before-amazon-approves-your--5e0bafb447694c0e3dc7ad9d?answerId=5e0bb010ae6e4d11696acc07
Do I needed to be approved in brand in order to add that product to my inventory?
How do I ship an item from my supplier if I'm gated?