There are two main ways to sum a range of cells in Excel:

1. Using the SUM function:

This is the most common and flexible method. Here's how to do it:

- Click on the cell where you want the sum to appear (usually an empty cell below or to the right of your data).
- Type `=SUM(` (the equal sign followed by SUM and an opening parenthesis).
- Select the range of cells you want to sum. You can do this by clicking and dragging your mouse across the cells, or by typing the cell addresses separated by commas (e.g., A1:A10).
- Close the parenthesis.
- Press Enter.

Excel will automatically calculate the sum of the values in the selected range and display the result in the cell you chose.

2. Using AutoSum:

This is a quicker option for basic summation:

- Click on the cell where you want the sum to appear.
- Go to the "Home" tab on the Excel ribbon.
- In the "Editing" group, click the "AutoSum" button (Σ).
Excel will try to guess the range you want to sum based on the surrounding data. If the selection is correct, simply press Enter to confirm.
- If the selection is incorrect, you can adjust the range directly in the formula bar before pressing Enter.

Both methods achieve the same result. AutoSum is faster for simple sums, while the SUM function offers more flexibility for complex calculations involving multiple ranges or criteria.