Board Thread:Support Requests - Designing Your Wikia/@comment-25648422-20150605112301/@comment-1192804-20150605123802

Two things: use Theme Designer.

Then you need to make the modules transparent, so look under modules and adjust the numbers. Specifically:

background: none repeat scroll 0 0 rgba(0,0,0,0) !important;

and

background: none repeat scroll 0 0 rgba(0,0,0,0.77) !important;