Is there a good tutorial on how to use Symbolize to create and use subscripted variables

Questions
1

I have tried to follow the examples in the reference guide Notation, Symbolize, and InfixNotation—Wolfram Documentation

However, I get errors even when pasting the code directly from the guide.

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2

You must not type Symbolize. You must use Symbolize from palette which opens when you load Notation. You can find more examples in the book

Malcolm Woodruff, “An Introduction to Mathematica for Civil Engineers” from the Notebook Archive (2025), https://notebookarchive.org/2025-03-cx2tujb

which I found on community.wolfram.com

3

Does this help? Personally, I avoid using subscripted variables in functions. But I know of colleagues who like to use them for presentation reasons.