This is the 2nd part of this Flash tutorial. Next, drag image0 onto the "images" layer, positioning it as shown below. Convert the image to an MC (F8) called "image0", selectin "export for actionscript". This will allow the image to be attached with actionscript, using the "identifier" as a reference.
Step 9.
Convert the MC again (F8) into another MC called "imageHolder".
Step 10.
Use the Oval Tool to create an oval on the mask layer, setting it to have the dimensions and positions as shown below. Right click on the mask layer and choose "mask".
a)
b)
Step 11.
The circle should now be masking the image, as shown below.