Our Theme Interface already supports ‘Font Awesome 4.7.0’. You can use the icons listed on the link.
To use the Fontawesome Icons you have use through Custom HTML. on page/post editor or the Blocks features you will find to use as Custom HTML.
Like for check icon you can use the HTML code <i class="fa fa-check" aria-hidden="true"></i> as mentioned here
For that you need to know some minor Basic HTML Concept. First let us know about how you created the Table. If you have created with WordPress Block (Gutenberg Feature) with Classic Editor then you will find the option to ‘Edit as HTML’ then you can past the fontawesome code to the desired table cell.