Hi Art,
Glad your octo is OK so far. You can feed the clams from Octopets, if you bought them. If not, try small hermit crabs, snails, pieces of thawed frozen shrimp or pieces of fresh scallop.
If you have a mature tank, it will have lots of amphipods and it may be eating these.
It's not unusual for an octo to be active on arrival and then disappear for a time.
When you figure out a name for him, let me know and I'll add him to the list of Bimac Siblings (first thread in this forum).
Nancy