onspace -c -S <SBSPACENAME> -p <PATH> -o <OFFSET> -s <SIZE in KB>
(optionally add -Df <DEFAULTLIST-OPTIONS> to add logging and so on, depends on what you want to do).
Afterwards, there are two ways:
First , put the name you provided earlier in the SBSPACENAME - Parameter in onconfig (Instance restart required). Every CLOB you create will automatically be stored in that sbspace.