VBA How to SUM result in last Row in columns (A:A)

Dear
I would like to edit code
At I can find Last Raw already but How to sum at Columns("A:A")

Worksheets("sheet1").Columns("A:A").Select
Cells(Rows.Count, 1).End(xlUp).Offset(1, 0).Select
ActiveCell.FormulaR1C1 = "=SUM(A:A" & LastRow & ")"
End

Please ad visor because not working
I am beginner

Thank you krab So I have many columns A,B,C,D,E,F==>O
How I set

Sub selectlastemptyrow()
Worksheets("sheet1").Columns("A:A").Select
Cells(Rows.Count, 1).End(xlUp).Offset(1, 0).Select ' row,colum

Columns("B:B").Select
Cells(Rows.Count, 2).End(xlUp).Offset(1, 0).Select ' row,colum
Columns("D:D").Select
Cells(Rows.Count, 4).End(xlUp).Offset(1, 0).Select ' row,colum
Columns("F:F").Select
Cells(Rows.Count, 6).End(xlUp).Offset(1, 0).Select ' row,colum
End Sub

WOWWWWWW Thank you krab success lawww for kindly support

Dear All
I would like to copy some and many columns in TG.xlsx file to V1Sum.xlsm how I do
Thank you krab

Private Sub CommandButton2_Click()
Dim TGColumn As Range, V1SumColumn As Range
Set TGColumn = Workbooks("TG.xlsx").Worksheets("Sheet1").Columns("A")=======> I need Colume A,B,E,F,G,J,K,AJ,AQ,AU some columns to need copy
Set V1SumColumn = Workbooks("V1Sum.xlsm").Worksheets("3G").Columns("A")====>How I do

TGColumn.Copy Destination:=V1SumColumn

End Sub