To add 10 minutes to a date/time value in Microsoft Excel, use the following formula:

In this formula, A1 is the cell containing the original date/time value that you want to add 10 minutes to. The TIME function takes three arguments: hours, minutes, and seconds. In this case, we want to add 10 minutes, so we use 0 hours, 10 minutes, and 0 seconds.

Here are the steps to follow:

1. Select the cell where you want to display the result.
2. Type the equal sign (=) to start the formula.
3. Click on the cell containing the original date/time value.
4. Type a plus sign (+) to indicate that you want to add something to the original value.
5. Type the TIME function with the arguments (0,10,0) to add 10 minutes.
6. Press Enter to complete the formula.

The result should be the original date/time value plus 10 minutes.