Where can I find more information on how exactly the following method works
and what it actually does? I found the single line of the documentation leaves a bit to be desired:
Class weka.associations.Apriori
public void buildAssociations(Instances instances) throws Exception
Method that generates all large itemsets with a minimum support, and from these all association rules with a minimum confidence.
Look at all the documentation, not only the method documentation tooltip in your IDE. You are missing out on a lot of the documentation.
Weka comes with a whole book, that will give you plenty of detail.
The Apriori class documentation also contains much more than that single line you quoted. You failed to access the JavaDoc class documentation; it's not the documentation that "leaves a bit to be desired", is it? It points to two publication giving the details on the algorithm.