Content Fragment Models not working in AEM 6.3.3
How to utilize Content Fragment Models in AEM 6.3.3
1) There is a known defect that will cause the Content Fragment Models tile from appearing in Tools > Assets.
Follow the steps below to fix this:
2) We must enable DAM Structured Content Fragments
3) Now you can complete method "Enable Content Fragment Models in Configuration Manager" in the 6.3.3 help page  referenced before. This creates a config under which you an then create the models.
4) if you are not using Global, you need to manually perform the step "Apply the Configuration to your Assets Folder" from  because the UI for this is not in AEM 6.3.3.
5) Follow the method "Creating a Content Fragment Model" in the document  and the rest of the information about editing the models, etc.
Result: Once you have done this, you should be able to go to the asset folder (in my example /content/we-retail) create a new content fragment, and you'll see the new model you defined in stage 5, or any models defined under your config.