How do I make tiles from tilemaps transparent

I've been searching around for some time now, trying to find a solution to how I can make tiles in the tilemap transparent. The tilemap I downloaded to test how they work has a white background (others with a green background), with tiles side-by-side, but when I enter a few of the tiles on top of my background image (in a different layer), I can't get the white background away from the edges.

Here's an example of how it looks like now:

I'm trying to make my first platformer game, and what I need is to have the tile work as the platforms that I jump around on, while the background makes the scenery for the level.

have a look at the x and y spacing in the tilemap properties

Yeah, actually, I tried with a different tilemap, and it was much easier to remove the white spacing from that one by using the x and y spacing in the properties of the tilemap. For the one in the image above, I just couldn't get it right, though. But that's fine - I've just switched to a different tilemap.

Thanks for the help - I got it working now

also look at http://www.mapeditor.org/

Open it in an Imageeditor (Photoshop, Gimp, whatever), select the white background color (in most programs are selection tools that work like the fill tool, select every pixel of the same color). After deleting the white area it should be transparent. Save the Image in .PNG or any Format that supports transparency.

Replace the Image in Construct with the new one and *BAM* transparent Background. ^^

Do you need to have an external editor to select the background and then delete it? It would seem that this would not be necessary / an extra step?