To rename a column, select the column header and hit "F2" on you keyboard. This will put your cell in Edit mode and you can modify the text. You can also just start typing without hitting "F2".
In excel, you can use =hyperlink function. "=hyperlink(link location, friendly name)" See example below. This will make a hyperlink to google but will only show the word "search".
=HYPERLINK("www.google.com","search")
And I don't know about SqareSpace blog so I can't help with that.
