First, read and follow this guide on How to install Smart IPTV App.
Once it is installed, You can study the button function guide below to understand how you can work with the app through remote controller of your device.

Guide to the Remote Controller function:

P+/P- and Arrow buttons – navigate through pages, groups and channels.
ОК, Wheel, Up/Down – load channel list in Play mode.
INFO, INFOx2 – show programme information.
Number Keys – direct channel selection. “0” – previous channel in Play mode.
BACK – hide channel list and info; go back to primary list.
RATIO, Q.MENU – picture ratio.
PLAY – reload window; STOP – relaunch stream.
PAUSE – show stream link.
RED – switch to DVB input and back.
GREEN – EPG (Electronic Programme Guide) + Archive (if supported).
YELLOW – All channels, show digital clock in Play mode.
BLUE – Groups, Constant Infobar.