Have you already had some years working full time (at least during tax seasons) as a tax preparer under close supervision of licensed professionals? If not, that's where I'd start.
As for material you can use to learn PTO, there is not a whole lot to go by. It is a robust product with a great price but it does have a relatively steep learning curve, especially for a starter, because it is primarily input sheet driven (and the ability to drill down from form view is extremely limited).
You may like to start preparing dummy returns to better understand the operation of PTO and make sure it is getting the result you expect, or if different, why that may be the case. Unless you print the return on paper or in PDF, there is no charge for creating and preparing returns with PTO.
This board and the PTO FB group (which I would encourage you to join) would be two of the best resources for your every day question - these are not your free research services but sounding boards to check your understanding and to learn from others' experience.
Intuit does publish articles about how input should be made and the various toggles for bigger topics; 199A is a recent example. You can use the search bar to find what you need and narrow the results with filters.
You may also find the following helpful:
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Still an AllStar
