If theBuy Buttonsales channel doesn't appear in theSales channelssection of your Shopify admin, then you need to add it before you can create a newBuy Buttonor embedded cart.
From your Shopify admin, clickSettings>Apps and sales channels.
From theApps and sales channelspage, clickShopify App Store.
If applicable, then log in to continue to the Shopify App Store.
From the Shopify App Store, search forBuy Buttonto learn more about the sales channel.