Plesk database association

I am using a Plesk control panel
I am not so familiar with this type of control panel
I Click on the domain name I want to work on
I then Click on the Wordpress link in the top right hand side of the Plesk panel
I then Click on the database tab - I see the current database name associated with this wordpress site

If I have another site in the httpdocs folder in a sub folder called wordpress2 with wordpress files
How do I associate a database with this second site

If I navigate to this site I get a error:
https://www.mainsitename.co.uk/wordpress2
"error establishing a database connection"

If I look at the database name currently associated with the site parent (If I am in the parent site - clicked on domain name) and click on the wordpress link in the top right), the associated database name is slightly different from the name in phpmyadmin
If I am in the parent site (click on domain name)  and add a database it is not being associated with anything

Sorry to be so vague but I am not sure how plesk is actually working
Help please?