It is based mainly on 3 chords:
     F          G          C
E|-------| e|-------| e|-------|
B|x------| B|x------| B|x------|
G|-------| G|-------| G|-------|
D|--x----| D|-------| D|-x-----|
A|-------| A|-------| A|--x----|
E|x------| E|--x----| E|-------|

(- = one fret)

And it also uses this one:
    Am7
E|---x---|
B|x------|
G|-------|
D|-x-----|
A|-------|
E|-------|

If you hold down these chords it is pretty east to pick up this picking pattern

Intro (x2)

E|------------------------------------------------------------|
B|-------1--------1--------1-------1--------------------------|
G|----0-0------0-0------0-0-----0-0---------------------------|
D|---3-3------0-0------2-0-----3-3----------------------------|
A|------------------------------------------------------------|
E|--1--------3--------0-------1-------------------------------|

Verse (x8)

E|------------------------------------------------------------|
B|----1----1-----1----1---------------------------------------|
G|---0----0-0---0----0-0--------------------------------------|
D|--0----------0----------------------------------------------|
A|-------3----------3-----------------------------------------|
E|------------------------------------------------------------|

Pre-chorus (x2)

E|------------------------------------------------------------|
B|----1---1---1---1---1---1---1-3--1--------------------------|
G|---0---0---0---0---0---0---0------0-------------------------|
D|--3---0---2---3---3---0---2--------2------------------------|
A|------------------------------------------------------------|
E|--1---3---0---1---1---3---0---------------------------------|

Chorus (x4)

E|--------------------3---------------------------------------|
B|-----1---------1-0h1-----1-----1-----1----------------------|
G|----0-0-------0---------0-----0-----0-0---------------------|
D|---0---0-----2---------3-----0-----2---2--------------------|
A|------------0---------------------3-----3-------------------|
E|--3-----3-------------1-----3-------------------------------|