As an example, we have the following screenshot of an IRF with a table and 3 columns. Notice that the value in the second column is cut off and you can't see the whole value.
<Please see attached file for image>

If you click the "Preview" tab of the IRF, in a browser that has developer capabilities (these screenshots are from Chrome), you can right click on the column and select "Inspect". Notice how it opens the html at the bottom of the screen showing the class for this column:
<Please see attached file for image>

There are multiple classes shown in the html above, but the class most specific to this element is the x-grid3-td-Var_1. So we will use that to alter the style.
Add an html field to your IRF has shown below:
<Please see attached file for image>

For the value of the html field, give is the following code. (Notice we are also modifying the class associated with the Table Column Header.)
<Please see attached file for image>

Click OK and then select "Save" and click on the Preview tab. Now the second column should be much wider.
<Please see attached file for image>