Enable the app embed in your theme
Turn on the Oxify app embed so the cart drawer renders on your storefront.
The cart drawer needs an app embed turned on so it can render on your storefront.
Shortcut: in Oxify, click Activate Oxify Cart in the Setup guide on Home. The Cart Editor also shows an Oxify Cart Drawer is inactive banner with an Activate button while the embed is off. Either one opens your theme editor on the app embeds panel. Make sure the Oxify embed is on, then click Save there.
Or do it by hand:
Go to Online Store → Themes → Customize on your live theme.
Open App embeds in the left sidebar.
Toggle Oxify: Cart Upsell & Gift to On.
Click Save (top right).
Reload your storefront and click Add to cart on any product. The drawer should slide in. (This relies on Open cart drawer on add to cart, which is on by default. You'll find it in the Cart Editor under Settings → Other Settings.)
Oxify's embed check (the Setup guide and the inactive banner) only looks at your live (published) theme, so turn the embed on there.
App blocks
The cart drawer only needs this app embed. There is no cart drawer app block to add to a section. Oxify's app blocks are for product page offers and product lists: Oxify: Bought Together, Oxify: Cross-sell, Oxify: Product Add-ons and Oxify: Product List. Product Page Upsells also use a second app embed, Oxify: Product Upsell. Turn it on the same way. The Product Page Upsells screen shows an Activate button while it is off.
Drawer still not showing?
See the troubleshooting article Cart drawer not showing.
The drawer also only loads once your cart settings have been saved at least once. If you have never saved them, open the Cart Editor, make a change and click Save.