The LiteSpeed Management Console (MMC) is designed to only use one thread, Enterprise Console allows user-settings.
To set the user-specified defaults, which will affect only backups initiated via Enterprise Console:
Choose Start menu Quest > LiteSpeed > LiteSpeed Defaults, or
In the Enterprise Console, expand the tree to display a SQL Server instance. Right click on the server name to display the Context Menu, then select LiteSpeed Defaults... Remember that you can have one set of default values per LiteSpeed Engine. Where multiple SQL Server instances exist on one machine, changing the defaults for one instance changes the properties for all instances on that machine.
Note: These settings do not affect the number of threads used by the backup assistant in the MMC Console (which is set to 1).