There are two options for recommending products in your cross-sell item block: Manual and Shopify Recommendations.
Manual Recommendations
The benefit of manual recommendations is that you control the exact products that are shown. This is a good option if you have 1-5 items you want to recommend.
To set this up, go into your Cross Sell settings.
In the Block settings section, make sure 'Specific Products' is selected for 'products to cross sell' then add the products in using the browse/search drop down.
Recommended Product Settings - display and styling
There are TWO ways to display your cross-sells: Stacked and Inline.
Stacked looks like this:
With Stacked, items are shown on top of each other.
Inline looks like this:
Items are shown in a side scroller.
FAQs
Can I add a discount to the cross-sell item?
Yes, you can. What you need to do is setup a discount in your Shopify Discounts (not in the Unicorn app) and make a Buy X Get Y for the cross-sell you want to offer.
E.g. Buy Product A and get 20% of product B.
You can then offer the Cross-sell (product B) in the cart and change the title to 'add me and get 20% off' and then the customer can benefit from this offer.