To reference a range of cells in a formula, you use the cell addresses of the first and last cell in the range, separated by a colon (:). Here's a breakdown:

Format:

`=SUM(A1:A10)` (This formula would add the values in cells A1 to A10)

Explanation:

- `=` : This symbol indicates the beginning of a formula in Excel.
- `SUM`: This is the function you want to use (in this case, SUM to add values). Functions can take cell references as arguments.
- `(A1:A10)`: This is the range reference, enclosed in parentheses.
- `A1`: This is the address of the first cell in the range (top-left corner).
- `A10`: This is the address of the last cell in the range (bottom-left corner).
- The colon (:) connects the two addresses, indicating all cells between them are included.

Additional Notes:

- You can select the range of cells you want to reference directly in the formula bar instead of typing the cell addresses manually. Just click and drag your mouse to highlight the desired cells.
- This method works for any rectangular range of cells. For example, `=AVERAGE(B2:F7)` would calculate the average of the values in cells B2 through F7.
- You can also use relative and absolute cell references within a range. Relative references adjust based on where the formula is copied, while absolute references lock onto specific cells.

By understanding how to reference cell ranges, you can create powerful formulas in Excel to perform calculations on multiple data points simultaneously.