Website Domain Re-Direct [HELP!] – Point to subfolder

Any help here would be really much appreciated, this is driving me nuts!

I have an account with a hosting server (https://www.nativespace.co.uk) which allows upto 5 mySQL databases.

In the root folder of this i have installed WordPress and use it for my work website (https://www.craigmarloch.co.uk).

I’ve now installed other WordPress installations into subfolders in the root directory (/barossa, /resonance, /m3). These are all seperate websites that i’ve designed for other companies.

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My problem is:

At the moment if i wanted to access the ‘barossa’ site for example i have to do so through https://www.craigmarloch.co.uk/barossa and access the admin panel through https://www.craigmarloch.co.uk/barossa/wp-login.php.

How can i use my purchased domain of https://www.barossa-ca.com to access the site instead of going through the craigmarloch address?

– Do i need to map the domain to the folder from the 123-reg site where the domain is registered? [If so, how?]
or
– Do i need to use the htaccess file to remap anything? [If so how?]
or
– ??!!?!

Cheers.