KeywordTests - Setting Random Name

Brand new to using testcomplete and I don't have coding experience.

I have a lastname field in my application and I want to record a test that will generate a random name.

I've used the Generate Data wizard to create a LastNameVar and FirstNameVar in my project. I then select those for the value where I'm trying to pass them in to my application.

However, when I reach that step, nothing is passed, and I receive an exception stating 'A row index must be an integer value'.

Not sure what I'm doing wrong.

Suggestions?