I don't know how long you have had this bike but... your rear pads look completely worn out!
as cyclist says try some salmon brakepads. somthing like these should be great on this bike. once they are installed you can change the rubber pad without fooling wiht the adjustment/alignment of the holder.
als brush your rims with some real fine grit sandpaper or scotchbrite and then wipe them off with rubbing alcohol to clean the off real good.
lastley have a bike shop adjust your brakes, since you are a novice. or see if you have a bike co-op that someone can teach you to properly adjust them.
http://www.ebikestop.com/koolstop_cr...pad-BR2170.php
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“One morning you wake up, the girl is gone, the bikes are gone, all that's left behind is a pair of old tires and a tube of tubular glue, all squeezed out"
Sugar "Kane" Kowalczyk