Hi Paul, welcome to ThemeForest! Please take a moment to follow the steps from the visual guide below, it will help you to successfully download/install/activate your WordPress theme.
Furthermore, for additional troubleshooting, the appropriate support section for your purchased item, if offered, can be found here
Just follow the instructions provided in the link above to interact directly with the author, where he'll be able to point you in the right direction. Your patience is appreciated. Thanks and good luck.