1. Select "Edit" at the bottom of your screen
A new row of icons will appear when you do. There's one icon for every section on your website, and every section can be edited.
2. Find the icon labeled "Contact"
Your website should have a contact section by default. Typically you'll see this section near the end of the row of icons, and down at the bottom of your website.
3. Select the "Phone Number" icon
Choose "Phone Number" to update your number. This will update your phone number everywhere on your website, not just in the contact section.
Here's a short video showing the full process: