Demo - Handle Box
Okay so you've uploaded the file into Design Space and it's in your canvas (if you don't know how to do that, please see the post on how to get started).
Here's how your layers panel should look
Note that everything came in grouped as it should.
Step 1: UnGroup, below is how it should look like after you hit the ungroup button
Now you will have two "groups", each section that has a drop down arrow next to it is considered a "group"
Step 2: Go through each one and change the linetype.
In the first group, I highlighted the first item. It says "Cut"because "Cut" is the default setting. Under linetype there's a drop down and a color next to it. The color is red, Red = Score. So change the linetype to score.
Moving on, I selected the next item in the group and look at the color under linetype. It's light blue, Light Blue = Cut. So I keep the type as "Cut".
The last item is Dark Green. Dark Green is just the base shape of the item you're cutting out. Note if you leave it as Dark Green, when you go to cut, it'll put it on a Dark Green mat. Does that mean you need Dark Green paper? No, it just means that anything that is colored Dark Green will be placed on the same mat.
That's the end of the first group. So now we go back to the top item to make sure everything is selected in that group and hit "Attach".
Now it should look like this
Hopefully that was easy. Once all your groups have been attached, then you can cut it out.