Symbol libraries

I have two questions about symbols...

1. I've created 4 symbols and placed 200 instances of them.
The symbols were originally created inside the CDR file. (and are still stored in it)
I have now exported the symbols to a CSL - how do I re-link the symbols to the CSL file?

2. How do I edit the CSL file so that the symbols are updated in the CDR file(s)?
I've opened the CSL file, edited the symbols and saved it.
Then I re-open the CDR file expecting the symbols to be updated - but they are not.