Once you have your campaign created, create an "Ad Group". In the picture below you can see where it says "+ Create New Ad Group".
Once you create an Ad Group, you can create other Ad Groups that all display under 1 campaign. This is helpful if you are promoting one website, but have multiple pages, or multiple products you want to promote all under that one domain.
I use the Ad Group feature a lot because I like to keep my main Ad Group running all the time, but I stop and start other Ad Groups when I have time to test and monitor.
