You're having trouble downloading the brain plots package? You should add a comment to that submission page, not this one. But if you just click the "Download Submission" link and unzip the file you download, all of the .m files should be in the resulting folder. I just re-downloaded that package to verify, and it looks OK to me...
The "data" variable contains the images for each trial specified by the design matrix (see above). That's what you pass to plot_brain2d or plot_brain3d. The 2d plots usually work better for viewing the synthetic data. This is because, whereas in real data "interesting stuff" often happens on the outer surface, in the synthetic data the sources are equally likely to be anywhere within the brain volume.
Let's say you want to generat a simple dataset with two trials, one unique source active per trial, and infinite signal-to-noise:
[data,cov_images] = generate_data(meta,eye(2),inf);
To generate 2d plot of first trial using default settings (requires installing http://www.mathworks.com/matlabcentral/fileexchange/36139-2d-and-3d-brain-plots), use:
To generate a 3d plot of second trial using default settings, use:
In each of the above examples, "meta" is the matrix included with the download of this package. (See documentation for additional details on the meta matrix.)