To find the time signature, you need to count how many beats are in one measure. ( add the values of the notes and rests in between the bar lines)
The upper number shows how many beats are in one measure.
The lower number shows which note receives 4 beats.
So for example, 2 has 2 beats per measure and a whole note receives 4 beats.
The time signature is written right beside the clef, so it can be seen on the left side of the staff