Something has instrumental value means that we value certain things not for its own sake, but rather because it helps us to get something else that we do value.
Example 1: During my freshmen year of college at Penn State, I was friends with certain people for sole purpose of being invited to parties. That friendship had instrumental value because I valued that friendship not for its own sake, but rather something I did value, meeting new people and having fun.
Example 2: Another common example I could think of was money. Money has an instrumental value for buying a phone.