Kathys,
The anchor is used to mark a place to which you want directly refer via a hyperlink. The dialog shown in the screenshot is exactly how to do it.
Select a text fragment that represent the desired destination for the CTA. Open that dialog and enter the name, for example cta-destination.
Then select the CTA and add/update the hyperlink.
If the CTA is referring to another page, then append the anchor name after the hash character (https://www.site.com/page#cta-destination).
If the CTA is referring to the anchor placed on the same page, then select "link to anchor in the text" option in the link builder dialog and enter cta-destination.