Add a new instagram widget

Follow the instructions here.

Install Theme

When you download the zip of the template, you have to extract the files that are inside. You cannot upload a zip file to Blogger.

Install Theme

Go to Theme -> click on the arrow next to Customize > Restore > Upload > select the xml file (Joy.xml).

Enable Responsiveness

Go to Theme -> click on the arrow next to Customize > Mobile Settings > check "Desktop".
The theme has its own CSS to make it responsive.