Genital Warts is mostly spread through having sex with a person who is infected with genital warts however it is still entirely possible to catch genital warts even when you're not sexually active or having sex with another person.
Genital warts can be spread through kissing or just plain skin contact with the infected person since genital warts are in the environment as well.
However you cannot get genital warts from sitting on a toilet seat that an infected person has sat on or through sharing clothes with the infected person.