Unless I'm misunderstanding the issue, the easiest solution is to move your frame in front of the other elements. Select the border, and from the main menu, choose Object > Arrange > Bring to front.
Or, for more precise control of the "stacking order" of your objects, for instance, if you don't want the frame to be the top-most object in your drawingbut still be in front of the overlapping objects, select the frame, which will be showing as "Selected Art" in the Layers panel, and move the frame in front of the objects. If you're not that familiar with the various indicators in the Layers panel in Illustrator, you can check out this short article: http://help.adobe.com/en_US/illustrator/cs/using/WS714a382cdf7d304e7e07d0100196cbc5f-62d8a.html
But if you want to actually trim the objects, the Shapebuilder tool (Shift + M), is a more intuitive way to work with Pathfinder operations. If you select the objects in question, the frame and the two other shapes, you can work with the Shapebuider to "merge" the overlapping pieces. There's a sweet video tutorial here that shows the use of this tool, which was introduced in CS5. http://tv.adobe.com/watch/learn-illustrator-cs5/creating-complex-art-with-the-shape-builder-tool-/