Ensure it’s not accessible by any clients, if you use a load balancer, you should take it off temporarily.
Connect to the MySQL Server via the command line:
mysql -u root
Stop the replication:
Now is a good time to make any changes you want to.
Check the status to confirm replication is running normally, and in most cases, catching up with the master:
show slave status\G;
If that went well, now’s a good time to put it back on the load balancer.