Special domain for a page

There is a plugin that does exactly this:

https://wordpress.org/plugins/multiple-domain-mapping-on-single-site

Anyway, it would be nicer to have things under control with an understandable few lines of script, so I’m still open to answers

Hata!: SQLSTATE[HY000] [1045] Access denied for user 'divattrend_liink'@'localhost' (using password: YES)