Adding New Songs
Written Guide
If a song doesn't show up when searching for it in ProPresenter, check the last time it was used in Planning Center
If the the "Since 3 Most Recent" only shows the upcoming Sunday service as it's "last date" that means it's a new song.
Planning Center
In Planning Center, select the song, and copy the CCLI number from the Song tab. Make note of the arrangement listed (normally called "Default Arrangement")