To begin, go to http://admgr.liebertpub.com.  Click the Options button on the bottom right of your screen:

Next, click on the Click here to configure the various ad zones link:

Next, enter a name for the new web property:

Enter the url for the new web property:

Click the check box next to Is Active to make it active and selectable:

Next, upload a logo for the new web property:

Next click save:

Next, add users by selecting them from the drop down box. Click the -> to add the selected user to this property. You do not need to hit the save button. Selections are auto-saved when you click the ->

Next to the user's name, you will also see a second drop down box for notifications. Choose To, Cc or Bcc for notifications or leave this drop down blank if the user doesn't need to receive them. You do not need to hit the save button. Selections are auto-saved.