If you want to keep the size of the chart as a whole, you cannot simultaneously increase or decrease the distances and keep the bar width constant because these variables are interdependent.
1. Drag the chart wider. Hereby, columns and distances between columns will get wider.
2. You can then reduce the width back to approximately the original width under Properties. As a result, you have reached a greater distance between the columns (with stable width).
If you only want to increase a spacing between two columns, you can do so by inserting a blank column in your linked Excel spreadsheet.
This results in a greater distance between two bars.