First click directly on Create if you do not already see the objects to select. Then click on the Circle.
Next, click on the A next to the circle in your main project area. A dialog box will come up and you will want to click on Positive and then click the check mark at the bottom right of the dialog box to enter these new properties of the circle.
Go up to your menu bar and click on Edit and then on Duplicate. This will make an exact duplicate of the first one. I do this just in case I happened to move the circle or resize it. If I create a new one and had moved the other, it'll be harder to line them up correctly.
Now you will click the A again to change the properties of this one. In the dialog box, click Negative and then the check mark at the bottom right corner.
Now you will click directly on Edit so you can get to the tools that edit your object.
You will want to resize the duplicated circle. Under "Create", "Edit" and "Sky and Fog", you will see a bunch of different things. The second one from the left is to resize your items. Put your cursor in the exact middle of the box, click and hold and move your cursor to the left. This makes the circle smaller. Moving to the right makes the circle bigger. You will want to make the duplicated circle just a tad bit smaller than the other.
Always make sure that the smaller of the two is negative and the larger is positive. This is what it should look like.
To make the opening all you have to do is make the smaller, negative circle taller than the larger, positive one. There are other ways to make an opening, but this is the simplest. Go back up to the resize tool and click and hold the tiny top square at the top of the line. Move it upward just a tad. Moving it up, makes the circle taller; moving it down would make it shorter.
Now at the bottom of Bryce, you will see a mini icon of objects. Click and hold on the circle. This is where you can select objects. You will want to select both circles, so click on Select all of Type.
Now you will Group the two circles by clicking on the G next to the objects.
You will now see a square frame around the grouped objects and you will see that the G changed to a U. Now click on the Render ball over to the left hand side.
You now have a hollow circle.
Here are a few objects that you can make hollow.