When there is a "/" it means just strum that chord once/quickly go to the next chord.
The Strumming pattern is pretty easy to follow along with.
Capo 1
Intro: Mute - then Am C Am C Dm C Dm Am7/C/Em/Am
Am C Am
Up with your turret
Am C Dm C Dm Am7/C/Em/Am
Aren't we just terrified?
Am C Am C Dm C Dm Am7/C/Em/C
Shale, screen your worry from what you won't ever find
C Fmaj7
Don't let it fool you
C Fmaj7 Asus2 Am
Don't let it fool you...down
Am C G E
Down's sitting round, folds in the gown
[ Tab from: https://www.guitartabs.cc/tabs/b/bon_iver/roslyn_crd.html ]
Am C Am
Sea and the rock below
Am C Dm C Dm Am7/C/Em/Am
Cocked to the undertow
Am C Am C Dm C Dm Am7/C/Em/C
Bones blood and teeth erode, with every crashing node
C Fmaj7
Wings wouldn't help you
C Fmaj7 Asus2 Am
Wings wouldn't help you...down
Am C G (unknown picking pattern)
Down fills the ground, gravity's proud
Am C Am
You barely are blinking
Am C Dm Am7/C/Em/C Dm
Wagging your face around
Am C Am C Dm C Dm
When'd this just become a mortal home? Now
Dm
Won't, won't, won't, won't
Won't let you talk me
Won't let you talk me…down
Will pull it taut, nothing let out
And that's all I got for now.