It looks like you might be trying to use multi-site...
https://wordpress.org/support/topic/how-can-i-have-two-wordpress-blogs-on-my-website#post-7367093
...and you do not need multi-site in order to have two WordPress installations at the same server and/or for having more than one set of tables in a given database. But unless you have a specific reason as drawn from an actual need for having more than one set of tables in the same database (such as for sharing users), it is better overall to have the sites' databases completely separate with each having its own SQL user.
I got the first blog set as 'wp_1', and the second as 'wp_2' of where it shows to do multiple installs on the same database (when installing and doing the 5 minute install thing).
But as I said, I'm having issues.
I would guess those are multi-site issues, so you might go back to your other thread to see whether the one who suggested that to you can help you get things working.