Highlighting In A Book

Garrell Calton said:

I want to highlight the word "first" in a particular book.  I have found every occurrence of the word "first", but is there a way to highlight every occurrence all at once, instead of each individual time?

You can do this using Visual Filters - see https://support.logos.com/hc/en-us/articles/360016747431-Create-a-Visual-Filter for some guidance.

The method Graham gave is your only option, outside of manually highlighting each word individually. 

For clarification: Using "visual filters" as described is not using the same tool as "highlights" and the feature is not available on mobile.