There are main two areas to check for entering your Settings.
Head to Setup > Receipt Settings on the management site. Here's where you enter your details to appear on receipts. There is a walkthrough at the bottom of the page if you get stuck.
Starting your Subscription!
The next step is to connect your iPad(s) to the Management Site but to do that, you'll need to have a working subscription.
By now you should know which plan to go for but if you're still unsure, pop through the support channel and someone should help you out!