Fans in Dreamball are made up of a few base entities, nothing Dreamball-specific. They're basically a trigger_push brush to give the push effect. The rest of the entities aren't required but are essential to look like a fan. As it's just a simple trigger based brush, there's no point writing a page telling you how to make them as you can read all you need here. Instead, assuming you want to use the same fan model setup as the official maps, just go into "Dreamball Dev Kit/SDK_Content/prefabs/gameplay" and you'll find 2 prefabs named 'fan_with_switch.vmf' and '3_fans_with_switches.vmf'. You can use these in your maps.
Note that if you place multiple instances of these prefabs you'll need to name the added ones again, uniquely. Also, if you rotate the trigger_push in your map you'll need to re-point the direction of the push. Do this by opening your trigger_push entity and in the Push Direction field point your fan with the black circle that has half a white line that is movable with your cursor. In your Hammer 2D grid named 'top (x/y)' use this as your direction base. Point the white line in the direction on the top 2D grid the way you want the trigger to push.