If I understand correctly, you wish to have all traffic that coming to http://www.primalhealthfitness.co.uk to redirect to http://www.primaltrainingclub.co.uk ?
I see these are both Webflow sites, so the first step is to make sure that both domains have been added to the hosting tab of site settings on the www.primaltrainingclub.co.uk domain.
After doing that, the next step is to set a default domain: http://help.webflow.com/faq/how-to-set-your-sites-default-domain
Once that is done, republish the site: http://help.webflow.com/lesson/publishing-your-webflow-site
To setup a page url redirect, i.e.
/old-page-url to /new-page
This can be entered in the redirect fields in the hosting tab of site settings: https://help.webflow.com/article/how-to-redirect-old-urls-to-new-pages-in-your-webflow-site-301-redirects
I hope this helps! If there are any questions, please let me know !