You say you went through the article - what exactly is the problem you're facing then? The article seems to lay it out pretty clearly?
i went to this path C:\Program Files\Tableau\Tableau 9.x and i didnt understand from there what to do? can you please tell me what to do after i reach this point.
You've linked to the full instructions, you aren't reading them completely!
The object is to create a connection-configs.xml file. The link you've provided literally covers everything you need.
Tableau already runs parallel queries wherever possible out of the box.
Configuration is only meant for cases when it's not working properly (I'm looking at you, Redshift) or you'd like to limit it (I'm looking at you, overprotective DBA).