The 413 Request Entity Too Large error happens when you try to upload a file or folder that is bigger than the maximum upload limit. It usually happens when uploading a plugin or theme folder using the upload options of your dashboard.

You need to increase the max upload size limit on your server. You can ask your server support to increase this or you can use the following code inside your child theme's functions.php file.

Insert the following code at the bottom of your functions.php file:

@ini_set( ‘upload_max_size’ , ’128M’ );
@ini_set( ‘post_max_size’, ’256M’);
@ini_set( ‘max_execution_time’, ‘300’ );

Please refer to the following article for more details.