According to Interesting Times, the official Ted Nelson newsletter, he first used the word in 1965
In a Vassar College Miscellany News article dated February 3, 1965, "Professor Nelson Talk Analyzes P.R.I.D.E.," written by Laurie Wedeles, Nelson is quoted as having used the word "hyper-text." (The full text of this article is available.)
The term was hyphenated in the article and is remembered as such by former Nelson student and Vassar alumna, Cynthia Fontayne, in an interview.
Unless there was an appearance in print during January, 1965, or unless Nelson is mistaken about when he coined the term, Vassar seems to have a good claim to the site of its first appearance in print.
Ted Nelson's long dream of the Xanadu hypertext system has recently been open-sourced..
The Miscellany News continues to be a newpaper which is, in the Vassar spirit, open to outsiders and the unaffiliated.