Can't upload image

Hello I am using Highend theme, bought it and uploaded on my wordpress, then loaded the demo content… Now I am trying to edit the Home page, when I try to put anything with picture, example the laptop slider, then click Edit it, to upload a photo, the green + doesn’t work at all, it does nothing when I click it.

Also if I want to put a single image and use the green + to upload image, does totally nothing… please help as I am building a website and have an end date to be done.

Regards