Keno's interface is quite simple. 

Use the Chip Size menu to change the amount you are wagering per ticket. 

The Keno Ticket is the large grid of numbers that dominates the play area of the Keno game. On it you will find the numbers 1 through 80. Left click on the Keno ticket to select a number. It will be highlighted. To deselect the number left click again. You can select up to fifteen numbers.

The Clear button removes all currently selected numbers.

The Undo reverses the effects of the last Clear.

Click the Play button to start a game of Keno once you are finished selecting your numbers.