To create or update an SPF record, you'll need access to your domain's DNS settings. Here are the basic steps:
Log in to your domain registrar's website. Navigate to the DNS settings or DNS management page. Add a new TXT record with the SPF data or update the existing one. Save the changes and wait for DNS propagation.
For example, a simple SPF record might look like this: v=spf1 include:_spf.google.com ~all.