Find the PHP.ini file in root directory.If you not see the file select the option “Show hidden files” then the PHP.ini file will be visible. After that add this code in PHP.ini
upload_max_filesize = 20M
post_max_size = 25M
memory_limit = 30M
Also edit .htaccess file and add this code
php_value upload_max_filesize 20MB
php_value post_max_size 25MB
php_value memory_limit 30MB
Another method is to modify the WordPress file wp-config.php or functions.php files, and paste the following lines of code
@ini_set( ‘upload_max_size’ , ’20MB’ );
@ini_set( ‘post_max_size’, ’25MB’);
@ini_set( ‘memory_limit’, ’30MB’ );
If you still having an issue I will refer you to a guide where you ca easily learn how to increase upload size limit