Plant vs zombies CAN NOT log in

I use samsung and play plants vs zombies. There is no log in option in the app. In the roght upper corner there is an ad links to sims game. In the right down corner there is nothing.  So game help guide foesnt meet the problem. All my process and purchases can go lost any time. Customer service doesnt understand the issue.  They say its in the right upper corner there us a cog wheel. But there is NOT... Pls help.