Did you have an existing override file here?
\includes\templates\YOUR_TEMPLATE\templates\tpl_product_info_display.php
If you did you need to "merge" the code to make it display with this file
If you didn't have this override file here..
Then rename the "SAMPLE_ADDITION_TO_tpl_product_info_display.php"
to "tpl_product_info_display.php" and upload
admin->configuration->Cross Sell Settings
Be aware there is some confusion regarding how many you need.
Most websites will be fine with just ONE as it can handle tens of thousands of cross sells
You ONLY need more, if you want to have a different text header that is shown on the cross sell
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