To find an author's h-index, start from the library's web page, Click on Databases A-Z, and search for "Web of Science."
Choose Web of Science Core Collection.
Search for the organization using the Select from Index feature and add another field. Search for the author using the last name then first initial with an asterisk.
Click on Create Citation Report on the right side of the results screen.
The h-index will be one of the statistics given on the right.
Problems
Searching a specific author in Web of Science can be tricky because not all journals enter an individual's name using the same format (some use initials, some use full names, etc.). Web of Science usually uses lastname plus first and middle initial. You may find multiple authors with the same initials. Adding the name of the author's institution can help. You may have to experiment to get the best results or contact a librarian for help.
Iglesias, J. E., & Pecharromán, C. (2007). Scaling the h-index for different scientific isi fields. Scientometrics, 73(3), 303-320. doi:10.1007/s11192-007-1805-x