OK then your question is really about frames rather than a mask .
Here are the steps I would do to get those images using the same 'mask' / frame.
1. I converted your image to a jpg (loaded png saved as Jpg and reloaded)
2. Applied a crop tool around the interior to get an approximate size of the image to be placed in that frame. In this case it was 331 x 197 pixels so I will use 330 x 200 (easier to remember).
3. I then take the image to be the inset and set a crop rectangle of 300 x 200 on that image and tick box Maintain Aspect Ratio.
4. I enlarge the crop rectangle to suit what part of the image I want. (this can be saved as a preset to speed up future crops) and apply.
5. The cropped image is then resized to suit the frame. (Image --> Resize)
6. Now to prepare your frame. I took your image(as jpg) and promoted it from background to layer to a raster layer.
Right click the layer to get the context menu and choose Promote Background Layer
7. I then choose all of your red area (magic wand set on Match Mode - RGB) and press the delete key and that part becomes transparent so I can see through to any picture beneath. . Then choose from menu bar Selections --> Select None
8. Now place the images together on the workspace and drag the image thumbnail from the Layers palette onto the Mask image. (This is a quick Copy and Paste as new layer) .
9. Lastly drag the image layer beneath the mask layer and use the Move tool for final positioning.