You CAN use your fingers for this song, but Relient k's bass player uses a pick.
If you use a pick it is easier to maintain tempo and play it fast enough.
The ... means that the note is repeated several times, just listen to the song.
If you know the tune well it is not hard.
intro/verse
-------------3...-----------------------------
---------3...----1...-------------------------
----3...--------------------------------------
----------------------------------------------
the chorus is the same thing but the rythym and tempo change...
all-in-all this is a pretty easy song. Good luck with the bridge, it is hard to pick out.
https://primoaccordo.net/relient-k/the-80s.htm