Q: Where can I get the tag for the RPC Portfolio for within article display?

A: The tag is displayed in the Portfolio list in the Portfolio manager - just copy-paste it.

Go to the Portfolio Manager, you will now see a list of Portfolios you've created. Each entry contains a tag for the respective Portfolio, just copy-paste it to your article.

Alternatively, you can use the RPC Portfolio editor button.

While editing a Joomla article, click the button labelled 'Insert portfolio' - now, a modal box containing a list of Portfolio will open.
Next, click the Portfolio you wish to insert into the article - the correct tag will automatically be inserted in the article.