How can I install the SIM card on Samsung Gear S(SM-R750)?

You can insert the SIM card provided by the mobile telephone service provider.

IMPORTANT : Only nano-SIM cards work with the device. The available features may differ depending on whether or not a SIM is installed.

a). Use the SIM ejector tool when you open the SIM card cover to avoid damaging your fingernail. 

CAUTION : Do not lose the SIM card cover and the SIM ejector tool.

b). Insert the SIM card on the inside of the SIM card cover with the gold-coloured contacts facing outwards. 

c). Place the SIM card cover on the Gear and press the cover to close it.  

After you install the SIM card, restart the Gear.  

NOTE : Ensure that the SIM card cover is closed tightly to prevent water and dust entering the device.