If you created and manage your website with Wix, you can add and manage your UET tag there.
From the top menu, select Tools > UET tag.
If you're using the new Microsoft Advertising navigation, from the navigation menu on the left, hover over Conversions and select UET tag.
To validate that your Wix UET tag is working, download and install UET Tag Helper. Go to your Wix website and verify that a UET event is received and that the Tag ID matches the tag you selected in Step 1.