LET vDatetime1 = now() // just an example, replace with something useful
LET vDatetime2 = now()-1 // same as above
SQL select STATISTICS.INBOUND_TRAFFIC ( $(vDatetime1), $(vDateTime2) )
Give the two datetime parameters proper values and make sure they're the data type that the package function expects.
You could ask your dba to show you how to call the package in for example sqlplus. That would give you a better feel for how things work.