I am learning a song and need help reading the music sheet. I think the bass clef is for piano? Notes show up one on top of the other. I am assuming a piano player would play both notes with two fingers simultaneously on the left hand. What do I play on bass guitar or do I not follow the bass clef for piano?
It's commonplace for the bass clef (usually left hand) of piano sheet music to contain more than one note. Usually, but not always, the bass guitarist will play single notes for their part in songs, because someone else is playing the other notes which make up the chords that are the backing. On bass guitars, often, playing two or more notes cause a muddiness in the sound - 6 string basses are better, as the top couple of strings are pitched higher, so one is the norm.
When the sheet music shows more than one note, you can of course play both or all of them on bass guitar; it's not difficult, but you'll probably find the sound is not too clear, so maybe stick to the lower of two or three. Otherwise, ignore that and play notes from the chord/s in each bar, singly.
One thing you can do is to use both hands and play by tapping the notes. If the song is written for piano, it might not be easy playable at the bass. It has more limitations, so you might find out that the song cannot be played on the bass.
But, try using both of your hands and see if you can press both notes at the same time.
Some examples of bass tapping: