Hey Andrew,
If you haven’t done any template customization yet, you can easily switch to the child theme. First, you need to backup your site first (files and database). Then, backup your Customizer settings. See https://community.theme.co/kb/customizer-manager/.
If you’ve made customizations, you need to account all files you’ve modified and then move them to the child theme. For more details, see https://community.theme.co/kb/customization-best-practices/
When switching themes (even the child theme), your menus and widgets might reset. Your current widgets might be moved to the Inactive Widgets area so you need to move them to the designated widgets area again. For the menu, you’ll need to assign the Primary and Footer menus again.
Thanks.