Bro.. ahead of Mangla u reach Mirpur and then take Kotli rd. You will pass cities/towns like Islamgarh, Chakswari, Rajdhani, Nar, Billi Porian..
Just after Nar/Billi Porian and about a few km before Gulpur city, you will see this view (above pic) of waterfalls from main road.. if u have to go down to falls (by foot) then the way is after Gulpur town. We stayed in Kotli and then headed back to Lahore next day.
You can also go to Kotli and then to Nakyal sector as someone was recommending to visit it as it is beautiful place but we were short on time so couldn't visit.