Each game has a how to play guide that includes the win lines, symbol multipliers and various types of information regarding bonus rounds and features that are specific to that game. As there are games on site made by various developers the how to play guides are not always in the same places.
The most common place is next to the buttons to alter the coin size and pay lines, either to the left or right of that bar. The button will take the form of an 'i', 'menu' or 'help' button.
However, the guide can sometimes be accessed by clicking on the in-game menu (the 3 horizontal dots), in there you will see an option for 'game info', click that and it will bring up all the game information.