well, first off you’ll need to know what theme you are currently using.
To find out, go in to Appearance -> Theme inside of wp-admin. Look for current theme.
Once you see what theme you are using, you’ll know where in the WordPress file system you need to go.
The wordpress file system is on your host server. Typically, you’d access this through FTP, either a local client, or in your hosts control panel.
Once you get access to the file system, the theme path is wp-content/themes/[yourCurrentThemeFolder].