Hi Alireza,
The Vs+ pins 5 and 16 are internally connected. The same goes for the Vs- pins 8 and 13. The part will work if you have just one of the pins of each supply connected to the external power, but to ensure optimal operation it is recommended to have both pins of each supply connected to your power source.
There is no need to have decoupling capacitors on each separate supply pin. I suggest that you follow the datasheet recommendation to connect a 0.1uF capacitor to pin 16 (Vs+), and another 0.1uF capacitor to pin 8 (Vs-). These should suffice for decoupling high frequency noise. 10uF tantalum capacitors should also be added, one for each supply, but these can be placed further away from the part.
I hope this helps! Please let me know if you have further questions.
Thanks!
Kris