Final answer:
The BNA Portfolios are accessed under 'indexes and finding aids' where users can click on 'Contents' for chapters or use the Index for non-electronic text navigation.
Step-by-step explanation:
The BNA Portfolios can be accessed by clicking on the headings under 'indexes and finding aids'. When navigating the online text, you can click on the Contents on the left side of the screen to jump to any chapter. Within each chapter, you can expand the chapter by clicking the plus sign (+) beside it, allowing you to dive directly into a specific subsection. Moreover, there is an alphabetical Index at the end of the text which is useful for finding information in non-electronic versions.