Installing grayscale maps on App Store SC4 in Yosemite

[humanleague 2]

I've found a bunch of map installation threads for Mac, but none which seem to help my situation.

 

I have OSX Yosemite, and the App Store version of SC4.  I want to install custom maps but have been struggling.  I tried that SC4 Mapper software, but it just will not work when I try to install it.  So I went with the grayscale map option.  

 

When I load SC4, and press Ctrl, Shift, Alt, and R, I get that elusive menu for finding files, but it's blank, with an inability to find files.  I think the screenshot is attached!

 

I read somewhere that one should try converting the JPEG to BMP.  That I have found to be seemingly impossible on Yosemite, much to my frustration (not even Preview will do it, and I even tried the pressing 'command' trick on the file converter.  Didn't work).

 

I have also tried typing the file path into the box on SC4, but that yields no results.

 

So the big question is, is there any way I can successfully install a custom map onto this version of the game?

 

 

 

 

 

[TEG24601 32]

Due to Sandboxing of App Store games, you must either place your .bmp file within the .appstore folder, or you have to use the full path for the location of your files.

 

You also have to enter the path in the Cheat bar, and just start with / (which indicates the root directory of your hard drive).

[humanleague 2]

Interesting, so then, does this mean I need it to be a BMP, and not a JPEG?

 

And how do I find this .appstore folder?