You can highlight cells based on a specific value in Excel using Conditional Formatting. Here's how:

1. Select the cells you want to format: Click and drag to select the range of cells you want the rule to apply to.

2. Go to Conditional Formatting: Navigate to the "Home" tab on the Excel ribbon. In the "Styles" group, click on "Conditional Formatting."

3. Choose "New Rule": A dropdown menu will appear. Click on "New Rule" to create a new formatting rule.

4. Select a rule type: There are various options for highlighting based on different conditions. Here are two common options:

- Format only cells that contain: Choose this option if you want to highlight cells that contain a specific text or number value.
- Use a formula to determine which cells to format: This option allows for more flexibility with formulas.

5. Define the rule (depending on your chosen option):

- Format only cells that contain: In the "Format values that contain" box, type the specific text or number value you want to highlight. You can also use wildcards (* and ?) for partial matches.
- Use a formula to determine which cells to format: Enter a formula in the formula bar. For example, to highlight cells that equal "apple," you would enter `=A1="apple"` (assuming your data is in column A). You can use various comparison operators like >, <, >=, <= for numbers or dates.

6. Set the formatting: Click on the "Format" button. This will open a formatting window where you can choose the desired highlighting options like fill color, font color, borders, etc.

7. Click OK: Once you've defined the rule and chosen your formatting, click "OK" to apply the conditional formatting.

Now, any cells within your selected range that meet the specified criteria will be highlighted with the formatting you chose.

Tips:

* You can create multiple conditional formatting rules for the same cell range to highlight different conditions.
* You can use more complex formulas for advanced highlighting scenarios.
* Explore the other conditional formatting options available in Excel for different highlighting needs (e.g., color scales, data bars, icon sets).