1. Launch Excel to open a blank worksheet or load an existing worksheet.
2. Click on an empty cell where you want the number series to begin.
3. Enter the starting number you want, such as '1.'
4. Click on an adjacent cell. If you want the number series to run across columns, click on the cell to the right of the one you just numbered. If you want the number series to run down, click below the first cell.
5. Type the next number in the series, for example, '2.'
6. Select the two cells by clicking and dragging from the first cell to the second cell. Your selection should have a black outline around it.
7. Hover your mouse over the bottom right corner of the selection until you see a black cross appear. Click and drag, either down or to the right, for as many cells as you need to complete your series. Excel will automatically fill in the remaining numbers in order.