Locate My Account in the header and select Share. Under the Share List(s) tab select the lists from the List Names and select which Organization Units you want to share with, then click on the Share Lists(s) button. Under the Share Segment(s) tab select the segment you wish to share from the list names column, and choose the Organization Units you wish to share with.
After sharing, the Shared details will appear below. To avoid sharing a list accidentally click on button relevant to that list and then click Submit button. See screenshot below for additional details.