I have a tablespace I want read only. I have spent countless hours creating the perfect demo set of tables filled with all the data I need. I did this one other time and all my data was overwritten by someone who did not know what they were doing. Is there a way to lock the tables to where they can only be read by the User I created for them??? Help Please

You basically want a set of tables that cannot be altered (updated, deleted from) by any other user thaen yourself.
What you should do is create two schemas (or user account as some people call it).
One schema, say A, is where you create and fill your tables. You give this schema a password you alone know.
Create a second schema, say B, which your normal users will use. Now from schema A grant schema B select privilege on the tables from schema A. After that log onto schema B and create synonyms for the tables from schema A.