Durham Topas Tutorials
There are various tutorial sets available for learning some of the Topas functionality:
For a simple set of tutorials go here.
For an extensive set of topas/jedit tutorials go here.
If you’re a jEdit user then browse through the .inp files in TOPAS_v*_Menus/Examples.
More detail and background theory is available in the text book “Rietveld Refinement: Practical Powder Pattern Analysis using TOPAS” by Dinnebier, Leineweber and Evans. More details from de Gruyter or Amazon.