Select the cell where you want to add a new cell
Right-click the selected cell
Click Insert
Choose Shift cells right or Shift cells down
Click OK
Select a row or column header to add multiple cells at once
Right-click the selected row or column
Click Insert
Use the Home tab
Click Insert in the Cells group
Choose Insert Cells, Insert Sheet Rows, or Insert Sheet Columns
Use the keyboard shortcut Ctrl + Shift + +
Select the range of cells first
Confirm the insert option when prompted