Well ..
You can do from the table (context) menu .. ALTER TABLE. You may change the charset for individual columns (clcik the option to 'show language options') or from ALTER TABLE .. advanced if you want to change the default charset of a table (but changing the defaut charset for a table- or a database for that sake – does not change the encoding of existing columns).
Please also read this FAQ: http://webyog.com/faq/content/34/152/en/my-special
-characters-display-as-_noisy_-latin-characters-in-sqlyog.html