Setup for a second phone line (FIOS)

I'm a long-time VZ customer. I went from single line to two-line, back to single line, and then to FIOS. I just added a second line. I'm not sure what I need to do to utilize the second line. Do I just need to change the wiring for the jack I want to use for the second line? Can I just buy a converter to plug into the jack to switch to the other line?

Thanks in advance for any guidance you can provide.