Can't find the sign up box nor change CSS font

Hi I've been struggling with various themes for a week now, trying others besides WPMU ones only to find out they don't work but I always have issues too with WPMU ones too. One thing or another doesn't seem to mesh in each theme I try.
E.g, now I'm on Business Features and even though I selected default CSS option, nothing changes, and also there is an option for a signup box but nothing appears when I click it.
The only thing I can think of is that I'm not installing the themes properly. I checked via FTP and all the child themes seem to be there but they may be in the wrong spots. I usually install themes through th dashboard. Thanks.