How to get my car to shift into gear on 1999 Volvo S80

My car was given to me and everything works fine except it won't shift into any other gear but park. It sat unused for quite a while what can I do to fix the problem

Asked by for the 1999 Volvo S80
There's a shift lock system the prevents you from taking the shifter out of park until you step on the brake. This system is malfunctioning and should be looked at.