Then when the input dialog box appears, drag your y column into the Response box, and the go back to the selection box and select your X Factor column. Right mouse click on it and select formula. This will allow you to create a virtual column which is the exponential of the X column. If you clear the formula editor when it comes up, and then go to the Transcendental category you will find the Exp function. Select it, and then click on your X column to indicate that it is the column for the Exp function to act on.
You can then use the new virtual column as your X Factor column in the Fit Y by X platform