@BigBen - thank you for pointing me in the right direction :) I have found what I needed.
It was really hard as I have never done any coding in my life and only did 5 hours of VBA online learning! Thanks, the script is below for anyone that may ever need it:
Range("A" & Rows.Count).End(xlUp).Offset(1).Select
ActiveCell.FormulaR1C1 = "PCxxx"
'this is inputting data into the last row with no data in the table in column A
Range("D" & Rows.Count).End(xlUp).Offset(0).Select
ActiveCell.FormulaR1C1 = "Userxxx"
'this is inputting data into the last row with no data in the table in column D
Range("F" & Rows.Count).End(xlUp).Offset(0).Select
ActiveCell.FormulaR1C1 = "ServiceCodexxx"
'this is inputting data into the last row with no data in the table in column F