Hi Brian,
Welcome to the Forums!
1. On Step 3 of 9: make sure you have Campaign as a Selected Field. Now move over to Step 8 of 9: and look for Opportunity - Campaign - to the left click on Edit and in the dropdown choose the Default Value for which Campaign you will be assigning it to. Also make sure it is a hidden field checking the box to the right.
2. On Step 2 of 9: there is a stock field there you can use 'CreatedDate' - again add that to as a Selected Field, move over to Step 8 of 9: make sure it's hidden. Whenever a Form is submitted that field automatically gets assigned with the CreatedDate for that Lead.
If the Custom Field you created is a DateTime field you can use that as well following the same steps.
Hope that was clear, if not let me know and I can elaborate.
- Mortaza