If you have already built your website elsewhere and are happy with it then it makes sense to simply transfer that website to your 123-reg hosting, and transferring it is simple.
The following procedure is also a good website management task to learn and carry out on a regular basis. We recommend you back-up your website regularly and always ahead of any major changes for your own piece-of-mind.
Back-up your existing website by making a local copy to your computer's hard-drive or an external drive like a USB stick. This is best carried out using an FTP client like Filezilla.
You can find out more about FTP and how to use it via our support articles, including What is FTP, How can I upload my website using FTP? and What are the most common FTP problems?
Using the same FTP client, log-in to your 123-reg hosting.
Copy across the files store on your local drive to the 123-hosting.
Check the site is fully functional by looking at your 123-hosting page in a normal web browser.