Run "setup" under app management from within Splunk either at the time of install or after.
a. Enter your CustomerID as the Username.
b. Enter your apiKey as the password.
c. Enter lastpass as the realm.
Decide if the default index main is acceptable.
If you desire a different index you should.
a. Copy the default/inputs.conf to local/inputs.conf and edit the index field.
Edit bin/lastpass-log.py in the main section to put your LastPass CustomerID into the username field
username = 'ChangeMeTOCustomerID'