Keynote slides orientation
You can specify a custom size for your slides by going to Document in the top right corner, it wil open a box on the right side of your screen and there wil be an entry regarding the size of your slides, the default is 1024 x 768.
Open this selector and you see "custom size".
If you enter 768 x 1024 in the resulting window the slides wil be in a vertical orientation.

ps. my keynote version is 6.2 and it is in dutch so I don't know what the menu items will be called in your version