If you want to load ACL only to Products and Libraries you can use the csv Loader like:
#AccessRule,user,domain,typeId,permission,principal,permissionList,state,parentDomainContainerPath
Example: <Windchill Home>\loadFiles\rule.csv
If you want to load Organization ACLs you have to use the XML syntax:
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE ProductConfig SYSTEM "standardX10.dtd">
<ProductConfig>
<AccessControlRule>
<domainName>/Default</domainName>
<externalTypeId>WCTYPE|wt.folder.SubFolder</externalTypeId>
<lifecycleState>ALL</lifecycleState>
<WTPrincipalReference isInternal="true">
<groupName>CHANGE ADMINISTRATOR I</groupName>
<groupType>DynamicRole</groupType>
</WTPrincipalReference>
<grantPermissionSet>
<AccessPermissionSet>
<permissionField name="READ"/>
</AccessPermissionSet>
</grantPermissionSet>
</AccessControlRule>
</ProductConfig>