It is much easier to embed the link into a posting, such as this example.
To do so use < to start, then a href="url_here" then > the word you want to highlight and then < /a > to close the comment. Obviously delete the spaces and extraneous words which I can't replicate without the instructions disappearing and this post being rejected, but there should be no spaces in the text between the <> except at a href which does require a space.
Badly composed links will be rejected by Blogger, so persistence is the key. The preview can also sometimes be difficult to read.