Related Posts - trouble installing

Newbie here trying to install the "Related Posts" plug-in and the script didn't work so I'm trying to follow the manual instructions but I'm lost. When the instructions say to

4. Just open your database in phpMySQLadmin and run the following command (cut & paste):

ALTER TABLE `wp_posts` ADD FULLTEXT `post_related` (
`post_name` , `post_content`

My question is where am I running this command from? When I open my database there is a series of tables such as "comments", "links", "options", etc.

Once I know which table to open where in the table do I need to put this code?

Am I to edit one of these with the code above? And am I to change any of this code to relate to my database or paste it as is?

Hope my questions aren't the same as "how far is yellow" - any help would be much appreciated.