Just replace the following field with your old and new url as well as the prefix if relevant in your case.

Then you just have to copy/paste the generated sql request in PHPMyAdmin (in the SQL Tab).

SQL Request:

update wp_options set option_value = replace(option_value,'http://old-url.com','http://new-url.com');
update wp_postmeta set meta_value = replace(meta_value,'http://old-url.com','http://new-url.com');
update wp_posts set post_content = replace(post_content,'http://old-url.com','http://new-url.com');
update wp_posts set post_excerpt = replace(post_excerpt,'http://old-url.com','http://new-url.com');
update wp_posts set guid = replace(guid,'http://old-url.com','http://new-url.com');