Oracle BLOB extract/view

I am having trouble finding the best way to display BLOB data from an Oracle table via PL/SQL.

I had limited success getting data out via
DBMS_LOB.SUBSTR() — but it is just numbers representing the binary code. The particular BLOB data thatI wish to extract and view is RTF (formatted) text. Additionally, Is there a way (function/package) to convert it to plain ASCII text?