To add a new data type to Tellor, you'll just need to define a new queryType. That's how you form a question so that Tellor reporters know exactly what data is being requested. You'll need to determine three things: a unique queryType name, inputs, and outputs. So let's say you want a query for getting the price of any asset in any currency.
In human-readable form, your question might look like this:
What is the price of asset in currency ?
Adding this query to a dataSpecs doc, you might define your query like this:
Name: SpotPrice
Inputs: