Here's how to use conditional formatting to format cells containing specific text strings in Excel:

1. Select the cells you want to format: Choose the range of cells where you want to identify and highlight specific text.

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

3. Highlight Cells Rules > Text that Contains: From the dropdown menu, hover over "Highlight Cells Rules" and then select "Text that Contains."

4. Enter the text string: In the "Format cells that contain the text" box, type the specific text string you want to identify. You can use wildcards like "*" (any number of characters) or "?" (a single character) for broader matching.

5. Set the formatting: Click on the "Format" button. This will open the "Format Cells" window where you can choose the desired formatting options for cells containing the text string. You can change font color, fill color, borders, or any other formatting style.

6. Click OK: Once you've chosen your formatting style, click "OK" to close the "Format Cells" window.

7. Click OK again: Click "OK" on the "Conditional Formatting Rules Manager" window to apply the formatting rule.

Now, any cells within the selected range containing the specified text string will be formatted according to your chosen style. This allows you to easily identify and visually distinguish cells based on specific text content.