how to set up a text link from a text word to a different position of text

Cross refs and hyperlinks are a very fussy process, and some of the key actions are a bit hidden. I am surprised that help page has essentially no useful links to the other steps and components, and that searches for 'text anchor' turn up nothing. (So: it's not just you. 🙂 )

For the simple case where you have a word or phrase on one page ("Snakes Alive!") and want to create a link to that text, using the same text, on another page, the process is this:

• Select the destination text ("Snakes Alive!" on the destination page.)
• Click on the 'hamburger' menu of either the Hyperlinks or Cross-References pane.
• Select "New Hyperlink Destination..."
• Select Text Anchor as the type, and modify the selected text as/if desired. This will change the actual cross-reference link text, though.
• Put the cursor where you want the new link to that text.
• Click the + button at the bottom of the Cross-References pane, or click on the hamburger menu and select Insert Cross-Reference.
• Select Link to: Text Anchor.
• Select the name of the text anchor you just created. (Or, later, any one that is in the list.)
• At the bottom of the menu, select "Link Name" as the option. (If you did not change the text above, it will be the selected text; if you changed it, that string will be used instead.)
• Click OK.

You should now have a link reading "Snakes Alive!" that when clicked in a PDF export, takes you to the same text on the other page.

Explore these menus thoroughly. Cross refs in ID are enormously flexible and powerful, which means they have endless configuration and option settings. There are also several elements, including hyperlinks and text anchors, involved without really being explained or differentiated. I know there are better references and how-tos out there; it's annoyuing that Adobe's own help system comes up blank on the topic.