Mysql replication is very well documented on mysql server web site and has a well explained howto that you can follow when you are setting up replication on your mysql databases.
You have to set in mysql server configuration file the log_bin parameter specifying the binary log file name that will be replicated across all the slaves. Mysql slaves take this binary logs from master and apply them to database; the problem I found is that Mysql server does not manage this binary logs expiration automatically, so if you are not careful and your database has a lot of changes your system can run out of disk space.
To address this issue, mysql has another parameter “expire_logs_days” that with you can specify the value in days of the binary logs expiration:
expire_logs_days = 5
max_binlog_size = 1G
In this config, 5 days after logs replication, mysql will automatically remove them. You have to adjust this value to be sure your hard disk is not going to run out of space and your slave has time enough to apply the binary log changes considering the number of days slaves might lag behind the master.
In the same way, you can use purge binary logs mysql command to purge old binary logs:
PURGE BINARY LOGS BEFORE '2008-04-02 22:46:26';