I created an entity-relationship diagram (logical model) and engineered it to a relational model. The tables were generated. Now I need to use them from the connection XE as you see in the picture.
The tables I made can only be seen on the data modeler design view in the "Browser", how do I get them on the connection "XE" to generate data dictionary, etc?

There are three possibilities:
If #3 is the issue, you would need to create them, possibly using the information in your Data Model - that is, you can generate the DDL/SQL scripts for those tables.
Then taking those scripts, run them while connected to the appropriate database/schema.
Disclaimer: I'm an Oracle employee and the product manager for these tools.