Are you trying to add some text between the slider and above the grid of posts? Please note that this is a fairly advanced customisation that requires some familiarity with HTML and basic PHP.
As noted above, the first step is for you to create a child theme.
Next, copy the parent’s index.php file to your child theme’s directory and rename it front-page.php. The code in the front-page.php file defines the content on your site’s front page. You should make changes to your front page in the code here.
One option is for you to add the content you wish as HTML directly beneath <main id="primary" class="content-area" role="main">
.
Another, more advanced, approach, is to edit the loop in this file so your static front page pulls in posts:
https://codex.www.ads-software.com/Creating_a_Static_Front_Page#Adding_custom_query_loops_to_front-page.php
Let me know what you think about the above or if you have any questions.