Hello!
I have made some research regarding this. I have found in the themes’ documentation (includen in the theme folder
/wp-content/themes/engrave-lite/licenses/ThinkUpThemes%20-%20Lite%20Documentation.pdf
), that you have to enable it in the WordPress admin under Appearance->Theme Options->Homepage, and put in a slider shortcode, which is generated by the plugin Slider Revolution.
I did not found that in the WordPress plugin repository, so I googled it. It looks like it is a premium plugin for 15$.
In the case you would not like to pay for that, I have done a little hacking for you. If you install some slider plugin that uses shortcodes (like [slider slideshow=”4″]), you can put that into the theme settings page, and it will appear, but there may be some CSS tweaking necessary.