Syncing Music from PC to iPhone7

I have some music on my PC that I want to transfer to my iPhone7.

I attached a cable to coordinate the two.

I tapped iTunes and tapped an icon for the smartphone in the upper left.

I clicked Music and then Sync Music.

There is an option to sync entire music library.

This is what I believe I want to do.

But when I tap the Sync Music option a box appears asking me if I actually want to do this because

" Music and movies synced to my iPhone will be removed and items will be synced to this iTunes library."

It sounds like it wants to remove the items I have on my iPhone and replace it with what I have on my PC .

I don't want to delete anything. I just want to move items from my PC to iTunes on my 7.

I can't drag and drop because it won't let me.

What am I doing wrong?

Thanks


This is the beginning of the process.........not mine......I found it online........




https://support.apple.com/en-us/HT201253

This is the error message:

When I go to.......... MY PC.......... Music .........Songs........

It says Local Only. What does that mean?