Shen isn't all that hard to play. Play safe and close to turret, have yourself ready for ganks and keep an eye out for your teammates' health. Until level, 3 don't make any moves to harass. Once you see an opportunity, walk up, press Q and then W at the last second before you get hit by an auto attack, try getting behind them, auto 3 times then E through the opponent back towards your turret. Get CS, buy Bami's cinder, buy Turbo Chemtank and boots, then you'll be set for later. At lv 6 keep an eye out for your team, if there's a near certain kill, just ult and get the assist, then TP back to lane.

Ideally you should always be splitting top and ulting over every time there's a proper team fight. Doing this will require the other team to have a player go to match, making every team fight a 4v5 (hopefully). When an engage is made, ult on the front line and get to their backline, use gargoyle stone plate as soon as you arrive, if the teamfight goes well and enemies are trying to escape, use Chemtank and sprint over to catch up and taunt, allowing more kills to be gotten. If you're at the teamfight before it happends, save ult for the case that your adc or mid is going to die. The shield will save them, and if it doesn't you'll hopefully arrive in time to use W and taunt to keep them alive.

Play safe at first, watch the minimap for assists and kill opportunities. In team fights just play smart and don't be too ambitious, you won't die. Good luck!