We have two "modes" for the campaign setup. By default, you will have Simple mode enabled. This means that you only need to enter a campaign name (which will only be visible for you) and upload or create an ad, and you are good to go. This ad will be shown once to every visitor that intends to leave your site.
On the top right corner, you can switch to the Advanced mode with 3 steps that allow much more settings to fine tune your campaigns.
(You can also switch "Advanced mode" to be your default one in "Website settings")