Okay it's pretty simple:
Make sure wifi is working,
Make sure you're signed into google play
Open google play,
It should download and you will be able to open the app drawer to use it..
If not, I'd try cold booting (Also called a Hard Reset) by turning it off, then holding volume down and pressing power, soon as the screen comes on release both and wait a minute for it to boot. (Ignore on screen prompts)
Then if not, you'll need to factory reset the tab. (Settings --> Backup & Reset --> factory data reset)
Then if not, call ASUS and complain that a basic function of your very expensive tab isn't working.