'but how does one 'Link Text'?'

Thisrefers to the text you want your link to appear as so rather than, for example :

www.pbslearningmedia.org/resource/xir779787fre/emperor-napoleon-i-contemplating-the-swo-xir779787-fre/

if you want it to appear as : a charming print of Bonarparte, in his Green Linnet costume

then you type (or paste) that text in the link text box and your link will appear as :

a charming print of Bonarparte, in his Green Linnet costume


Do check if the link works before posting. In this case the link you posted above goes to a 404.