In order to use this code, you have to do a few things.

1. You have to change the dbname, host, username and password.
2. You can customize the table by changing, deleting or adding new fields.
3. Go to your WP Admin Backend
4. Click on Tools -> Theme File Editor
5. Click on your desired Theme or don't if you want to use the active Theme
6. Click on theme functions on the right side of the Site
7. Go to the bottom of the code
8. Paste the code you've adjusted to your needds
9. Click on save
10. Go to the Page where you want the table
11. Add the shortcode [sqltable]