If you have had any sexual contact (manual stimulation, oral stimulation, genital stimulation, and/or anal stimulation any of those with or without penetration) then that is how you might have been exposed any/all strains of HPV. It is entirely possible to be exposed to HPV without having vaginal intercourse.

You cannot get high risk or low risk HPV (20+/100 strains) from hand shaking. It is possible to get a strain of HPV that affects the hands that way . . . but those are not the same strains that affect the genitals (oral, anal, vaginal, vulvar, cervical, penile).