How to use the multiple instance subprocess

Hello, I am wondering how to use the multiple instance sub process. the documentation:
https://access.redhat.com/documentation/en-us/red_hat_jboss_bpm_suite/6.4/pdf/user_guide/Red_Hat_JBoss_BPM_Suite-6.4-User_Guide-en-US.pdf
barely mentions how to use it. For example the "Variable Name" will tell jboss where to store the element of the list during run time, but I can't fidn anything like that by looking at the properties of the multiple instance sub process. Could someone tell me how to use this sub-process?