If you are planning to make advanced changes to the Olympus theme (mainly the functions.php file), the best way to do that is via a child theme. Luckily, we have already prepared a nice sample Olympus Child Theme for you, therefore you do not need to install unnecessary third-party plugins to create it.
Click the button below, you will be redirected to a GitHub page, from there, click the Code button and Download ZIP, then you just need to install the theme to your site via your dashboard, click Appearance > Themes, click Add New at the top of your screen and upload the zip file.