Version 6.0 of the theme includes some changes to the internal names for colours so it may be necessary to select some of your colour choices over again. As there will be at least one additional option it will be necessary to go into Easy Theme Options and 'save' regardless of whether you want to change anything else.
The download is in the format of a zip file. To install the theme go to your WordPress admin menu. From the menu choose Appearance and then Themes. You will see a screen showing your installed themes and at the top there is an Add New button. Click on that and on the next screen you will see an Upload Theme button at the top. Click on that and you will see the instructions for uploading the zip file you have downloaded. Once the theme is uploaded you will be able to activate it.