Need help putting music from Macbook to old iPhone

I'm just going to use the old iPhone as an iPod.

When I connect the old iPhone to my laptop, two options come up on iTunes: Set up as new iPhone and Restore from this backup.

This may seem like a stupid question but last time I tried something like this with my old laptop I somehow managed to delete all my songs from iTunes so I want to make sure I do it right this time.