Content Block link to another website

Hi,
I have just started working on a website, have installed a new theme that on the front page has blocks which include the feature image of the page, basically a portfolio. (here is the theme https://www.templatemonster.com/wordpress-themes/43003.html)

I am wanting to have some of the blocks linking to another website, for example, one i would like to link to Facebook with the picture being the facebook icon.

I cant work out how I’m meant to do this, I realise it will involve some extra coding but I was wondering if someone could point me in the right direction as I’m really not sure what i need to do.

Thanks!