Adding RBL to SA

[Pete]

I am exploring the ways of BL checking in MS and SA, i know how to
add/remove BLs availabel to MailScanner - But i cant work out how to add
them to SA 2.63 ?

I use SA RBLs only, none in Postfix and none in MailScanner.

I  guess i add them to local.cf or spamassassin.prefs.conf - but again i
dont know how - i want to add sbl-xbl.spamhaus.org
Another question i have is regarding 50-scores.cf - the formats of
scores for BLs in there is
score RCVD_IN_BL_SPAMCOP_NET 0 2.25 0 1.50
What does this format represent? Can i just grab the score
RCVD_IN_BL_SPAMCOP_NET as a straiught copy from this file to
spam.assassin.prefs.conf and add my own score? eg score
RCVD_IN_BL_SPAMCOP_NET 3.5 ? or shall i follow the 50_scores format ?

thanks in advance.

Pete