Click on the list tab. Select a list, then click on "Segments"
You can also click on the 
button under the list title.
In the news window, click on the 
button
In the window below :
In the blue area, you can choose the listupdate langs set en=s) you need to create this segment.
In the red area, you can add conditions or conditions groups.
Be careful !
If you create a multi-lists segment, the contact number displayed in "Contacts present in this segment" only concern the selected list, not all the lists.