You can use a domain that you purchased from 123 Reg to point to your OfferingTree site by setting what is known as a CNAME record. Here are instructions from 123 Reg to set up a CNAME record: https://www.123-reg.co.uk/support/domains/how-do-i-set-up-a-cname-record-on-my-domain-name/
Start by logging in to your 123 Reg Control Panel.
From there, select your desired domain from the drop-down menu within the Manage Active Products section and click Manage.
Alternatively, you can scroll down to the Domain names section and select the relevant domain name from the drop-down menu. Once selected, click Manage.
Scroll down to the Advanced Domain Settings section and click Manage DNS.
Select the Advanced DNS tab near the top.
On the next page, create a new record with the following information:
- In the Type field, select CNAME from the drop-down list
- In the Hostname field, enter the text www
- In the Destination CNAME field, enter the text customdomains.offeringtree.com
Once done, click Add to save the new record.
Additionally, we recommend adding a redirect so users that type in your domain without a www prefix are redirected to the www version of your domain. For example, if your domain is example.com please add a redirect so example.com goes to www.example.com. Here are instructions from 123 Reg to set up a redirect: https://www.123-reg.co.uk/support/domains/how-do-i-add-302-temporary-web-forwarding/
Use a 302 redirect and pick your domain. For the destination URL, use http://www.yourdomain.com (replacing yourdomain.com with your actual domain). For the "WWW redirect options", select "Do Not Redirect www"