How to Add Autofill to an Excel Spreadsheet

1. Open Excel 2010 and click the 'File' tab. Select the 'Open' option. Browse the files and locate the workbook. Click the workbook and the 'Open' button. The workbook opens.
2. Click the worksheet where the autofill will be added. Insert a column adjacent to the worksheet data. For example, if your data resides in cells A1 to D20, insert a column before column A. Do this by clicking the A column header. Right-click the column header A and select 'Insert.' A blank column appears to the left of the data.
3. Insert the number '1' in the first cell, A1, adjacent to the data. Insert the number '2' in cell A2. Highlight cells A1 and A2. Notice the black square in the right corner of highlighted cells. Move your cursor over this square and notice it becomes a black ' .' Click and drag the plus down in the spreadsheet. Autofill fills in the remaining numbers of the sequence. When you have reached the desired end result, stop dragging.