it will let me browse all the way into the Spark folder but when i get there the only thing that isn't highlighted or available to choose is the application, the one i need.
This is our fault. Spark is a bundled app (actually a folder that only looks like an application), and Live doesn't know how to work with bundles yet. We hope to fix this in the next major version.
For now, you can work around the problem by making a symbolic link to the actual application file inside the bundle folder. Unfortunately, you need to go to the Terminal for this.
Open the Terminal, and cd into the Spark folder. For example, if you installed in the default location in /Applications, type this:
cd '/Applications/SPARK ME 2.5'
Now make the symbolic link:
ln -s 'Spark ME.app/Contents/MacOS/SPARK ME' Spark-Link
Now go back into Live and choose Spark-Link as your sample editor. That should work.
Sorry for the inconvenience.