OnSong is designed to detect chords and then place them above the associated lyrics by default. However you can change display preferences that will display chords in line with lyrics. Keep in mind that this requires the chords first be detected by OnSong to work.
Show Chords Inline with Lyrics
Open the Utilities Menu by tapping on the gear icon in the Menubar. Open Settings and choose Display Settings > Song Formatting > Chords. Locate the Chord Position option and change to Inline and tap Done. This will reload the song viewer and place your chords on the same line as your lyrics.
Show Chords Above Lyrics
If you accidentally enabled this feature, you can always revert to the default display preferences. To do this, by opening the Utilities Menu by tapping on the gear icon in the Menubar. Open Settings and choose Display Settings > Song Formatting > Chords. Locate the Chord Position option and change to Above and tap Done. This will reload the song viewer and place your chords above the lyrics.