mySQL database on a different server, can’t connect to it

I’ve uploaded Worpress to my domain, but the mySQL database I have set up isn’t in the same place, so the default setting “localhost” doesn’t work. I’ve tried changing the location of the database as per where my hosting comapny says it is (I can connect to the database using phpadmin OK with the following url https://mysql.ukfast.co.uk)

define(‘DB_HOST’, ‘https://mysql.ukfast.co.uk’)

But I still get the error –

This either means that the username and password information in your wp-config.php file is incorrect or we can’t contact the database server at https://mysql.ukfast.co.uk. This could mean your host’s database server is down.