I have a userform with a MultiSelect listbox. How do I write a code to use
the item(s) selected by clicking a CommandButton on the same userform?

What I am trying to make happen is for the selcted items replace the entry
in the D column of the origin WS("Complete Listing") with the name of the WS
from which the UserFrom is activated. Then it would copy the rows A-F and
paste them in the WS it was activated from starting in row 9.

Here is what the code looks like now.

Private Sub UserForm_Initialize()
' Identifying elements
Dim ListBoxRange As Range
Dim LastRow As Long
' Identifying which sheet to pull info from
With Worksheets("Complete Listing")
'Telling it to count to the last used cell in column "F"
LastRow = .Cells(.Rows.Count, "F").End(xlUp).Row
'Telling it to set the range from A4 to F(LastRow)
Set ListBoxRange = .Range("A4:F" & LastRow)
End With

'Operations on the item checkout listbox
With Me.ListBox1
'Clearing data from the list
.Clear
'counting the number of columns
.ColumnCount = ListBoxRange.Columns.Count
'telling it to use the range set above for the listbox
.List = ListBoxRange.Value
End With
End Sub