If you want to add ads you need to sign up on an ads network, eg; google adsense, adsterra.
When you have been approved you can copy the given ads code into your "banners" which you will find when you log in to your site, under "dashboard" settings -> "banners"
Setting a new homepage cover photo simply head to your dashboard -> settings -> homepage and upload a new cover photo -> save settings (you can have multiple photos at once if you like)