Hi there KJ!
Don here from Shopify!
If you are using any of the free, Shopify-built themes you can enable order notes on your cart page by following the steps outlined in that guide. :)
If you are using a paid, third-party theme then you can get in touch with your theme's developers to see how they might be able to support this functionality.
You can also always reach out to us via our support site if there's anything else we can help out with. :)
All the best!
That's great however my site on the Debut Template does not have a cart. We only sell one product so all I have is a checkout page. Please advise.
Take a look at www.CustomTentDepot.com