WordPress will automatically show the maximum upload size when you are uploading images form media and there are many way to change Media file upload size.

1:By theme function.php file

@ini_set( 'upload_max_size' , '70M' );
@ini_set( 'post_max_size', '70M');
@ini_set( 'max_execution_time', '500' );

2: By PHP.INI file from your hosting cpanel dashboard

upload_max_filesize = 70M
post_max_size = 70M
max_execution_time = 500

3: By .htaccess file in the root directory of your website.

php_value upload_max_filesize 50MB
php_value post_max_size 50MB
php_value memory_limit 50MB