How were you able to install the Petro wallet?
Go here
http://www.elpetro.gob.ve/ and scroll down down down... you will find the wallet to download for Windows, Mac and Linux. iOS and Android are not available yet.
Not sure why but I keep receiving this message when I try to run the PetroWallet file "This app can't run on your PC". I currently have Windows 10 installed on my PC.