Tilesets and gimp2

Trying to re-range tile sets on gimp2. The ones I got have a green background to them, when I delete that, it goes to white. Is there way to get that transparent background on that picture of tile set?

When opening a new project, under "advanced setting" you can choose "Fill: Foreground color, background color, transparency" and choose transparency.

in an existing project, you can change a particular color to "alpha" which means alpha channel (transparency.)but that gets tricky.

Instead, go to layers - add alpha channel

and then select all of the green color and then edit>cut the green out and instead of white being left behind, it will be transparency.

(On new projects Levi is right, just select transparency from the start.)

thanks you two. I knew about new projects but existing ones were toughy