I tabbed this listening to the song and it is quite simple.
(This is my first tab)
Tuning: Standard
[ Tab from: https://www.guitartabs.cc/tabs/r/rihanna/skin_tab.html ]
e|----------------------------------------------|
B|----------------------------------------------|
G|----------------------------------------------|
D|----------------------------------------------|
A|------3--1-------3--1-------------------------|
E|--3~---------3~-------------------------------|
~ - Let it ring
Just repeat it through the whole song.
HOPE YOU ENJOY!