The Ruleset Maintenance wizard helps you copy rulesets and ruleset versions into new versions, merge several ruleset versions into one version, move rules out of one ruleset into another, or change a ruleset version's number. Select the Designer Studio> System >Refactor > RuleSets menu item, then click Copy/Merge RuleSet to start the wizard.
Use the Move operation to rename a ruleset: the process moves the rules from the existing ruleset into the new ruleset you specify, and then deletes the source ruleset.
found in the help
This will not amend any associations to the former ruleset..., so you may need to go through and manually do this afterwards