I'm creating a link - what should I put in the anchor field?

The anchor field is only used when you're making an internal link to somewhere else in the page (like using Bookmarks in Word). Unfortunately, anchors can only link you to somewhere in the same section so it's of no use in a long page that's been broken up into multiple sections - Tactuum have been asked about changing this but apparently it's not technically possible because of the way page sections are set up.