This song is so easy and it is one of their best songs.
The strum patern is just up-down-up.
After you have done this you have to stop the strings from ringing by just lightly touching the strings(staccato).
Put the capo on the 4th fret(capo iv).

Chords (0=capo on 4th)-
Am-x02210
Em-022000
E-022100
F-133211
G-320003 or 355433
C-332010 or 032010
C/B-x20010

(x1=up-down-up)

Intro-Am x4
Verse-
Am x4  
Em x4            do this twice
E x4       /
Am x5  / 

Chorus-do same as verse except change chord just before the last word in the sentence.

DoVerse again and then chorus.

Bridge-
Strumming- up and down
F
G
C
C/B
Am
F
G
E

(x1=one downstrum)
Instrumental-
Am x1
Em x1
Ex1
Am x1

Do verse again but only do it once.

Chorus again.