Increasing upload_max_filesize but where?

Installing a theme I received the following error:
“Some of your server settings do not meet the requirements for installing the sample data. Please, consult with your hosting provider on how to increase the required values.
Server Settings Current Required
upload_max_filesize (Mb) 2 8″ where 2 is the present max and 8 the desired.

I have been told I should add the following to a file in my public folder, perhaps a php.ini…> Or can it be added someho to the wp-config.php?

I am told I should add this: upload_max_filesize=6M
post_max_size=8M