Creating a campaign that is ready for sending is easy:
1. Create new campaign
2. Go to the campaign
3. Drag a recipients list from the left onto the canvas (the big empty space)
4. Click "New Segment" under the minimap in the upper right corner
5. Click on the dot of the recipients list (you will now see a wire under your mouse pointer/finger)
6. Drop it on the right dot of the new segment.