Do you mean DataGen test step or data source? Both can be used with any other test step. You can define properties in DataGen data source (or test step) and corresponding data generator and refer them in other test steps using property expansion.
I am confused on how to setup the datagen step. My api gets FINANCE COMPANY data and has columns like id, createdBy, createDate, lastModifiedBy, lastModificationDate, financeCompanyNumber, dbaName, legalName
When I run the api, I get an id of 8ac498b41548787001154daf7bcd0046 for example that is coming from our db.
I am supposed to create a datagen teststep and create properties that match my columns? Then use property expansion?
Exactly, so define property for each column and create data generator for each property. I would suggest to use DataGen data source (in Data Source test step) for this. For example, you can use Guid data generator for ID, Date generator for createDate and lastModificationDate etc.
And then use property expansion in futher test step with GET REST request, you can right click in request editor (parameter table) and click on 'Get Data', choose the property in data source test step to insert the property expansion expression.