Where is the option for me to sync only 1 way rather than merge bothways?

I recently got a new PC and so the fresh iTunes installation doesn't have the playlist I have on my iPhone. After I connect my iPhone to iTunes all the music got wiped out except those that I bought via iTunes. Each time I sync for each generation of iPhone and each generation of PC always wiped out the playlist and songs.

How do I avoid this and which configuration I can set more specifically to sync 1 way from iPhone to iTunes before the sync already happens soon as I plug my iPhone? or at least how to leave the playlist on my iPhone alone until I want to... but alllow me to sync specific songs/playlist i Tunes to my iPhone?