Different drop shippers have different setups but usually you can choose to credit your account, or, you can simply leave it empty and pay for each item as you sell it. Once you've created an account, all you need to do is grab the drop shipper's provided photos and product descriptions for the items you wish to sell and list them on eBay or your website. After you make a sale and receive payment, log into your drop shipper account, select the product you have just sold and take it through the checkout and pay for it. Enter the buyer's shipping details, and the drop shipper will package it up and post it.
If by license, you mean business license, occasionally you may run into suppliers who want to see a business license before they will sell to you. These suppliers will generally have large minimum orders and wish to determine that you are serious about purchasing their goods. Getting a business license is fairly straight forward. You need to contact your local court house or country clerk's office and they will direct you to the person you need to speak with. Some states will charge a fee for a business license application.
Please note that the majority of the suppliers on SaleHoo will NOT require a business license before they sell to you.
All the best!