You can use the Flexible width option to adjust the number and width of columns as the text frame is resized. Columns are automatically added or deleted when the maximum column width is reached as the text frame is resized.
Choose Flexible Width from the Columns drop down list in the Text Frame Options dialog box (Object > Text Frame Options)
Auto-size text frame options make it possible to set up a text frame so that it is automatically resized when you add, delete, or edit text. To access the Auto-size options, do the following: