This symbol is called a quarter note rest. It means there is one count of silence. Do not play any note. Small counting numbers are placed under rests.
A dot placed above or below a note tells you to play it staccato. Staccato means to play a note short and separate from other notes. To play a note short, lift your finger off the key (or your foot off the pedal) as quickly as possible. If a chord is to be played staccato, the dot is placed below the lowest note in the chord.
Practice each part separately before playing them together.