The previously released version of the theme, 6.0.2, has been around for some time, and indeed 6.1.0 was built in late 2018 but never made available for installation. The significant difference between 6.0.2 and 6.1.0 is that the 'panes' on the front page were tripled up on to add flexibility to the layout. 6.1.1 corrects a bug where the H1 background wasn't being applied to posts or search results, and also corrects the colour of the H3 headers in the search results (they are links so are intended to be in the standard blue link colour used throughout the theme, and they are not intended to use the standard H3 foreground colour).
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.