Matrix battery or fuse problems

2005 Toyota Matrix, 81,152 miles, v4. I was trying to install a new audio system today (two 12" subs, an amp, & a new head unit) & everything was going well until I ran out of time & had to pick my girlfriend up from school. I already had the battery wire connected to the + terminal & running to the amp & the directions I was given didn't say anything about when to connect the fuse to the wire's fuse holder (or so I thought) so I just put it in & left. Then the next thing I know, my head unit, interior lights, & clock weren't working. Did I blow the fuse? Or did I mess up my battery? What do I need to do?