So to do this, you need to do a few things. First, create a hidden page on your site that will contain these store items. you can hide pages on your site by clicking on the eyeball icon next to it on the Edit navigation menu. People can still see it but only if they have the direct url to that page. But it won't show up on the navigation anymore.
With me so far?
2. On your form, if you click on it, you'll see a button at the bottom where it says "Confirmation Message." click on the edit button. There, you can say something like "Thanks for registering and for your information. We will use this information for your order. Simply click here to finish ordering" and that will have a link to the hidden page that you created earlier.
This will make sure that they fill out the form completely before ordering.
Does that make sense! I hope it helps with this.