Cannot install theme on WordPress

Hi
I posted a Message yesterday, but now I do not find it, so I try it once again and try to rmemeber where I posted it……………
Here’s the thing: I purchased a King Size theme from Themeforest (zip-format), and downloaded it on my computer. But when trying to install it using the zip-tool in WordPress, it will not install. I have my own domain (Tores-side.com)
I have written to the Authors, which I earlier had a good “conversation” With, but after four days and a follow-up mail, I have got no answer from them.
Can anyone help me here ?

Tore