How to make changes to the database schema? I am trying to follow edits made in a php file to patch a module  and the instructions just say "In your database schema add this", which I could do if I knew where to find the file. When I look up drupal database schema it shows a map which doesn't help me to find the file. What do they mean exactly by in your database schema and how can I access this file in terminal? Is it by editing a table in the database? 

I can find the other file alright to edit in /includes/database/mysql/schema.inc file but just not the specific module one.

The instructions for this vchess module patch are here
Your database schema literally just means the structure of your database. It sounds like you're being instructed to manually make a change to this e.g. to add a column, which you could do in something like PHPmyadmin.

Normally a module's database schema is managed in its .install file. The initial schema is defined in hook_schema() and any changes are automated with hook_update_N(), but it sounds like you're being asked to make manual changes instead. Be careful!