The key to reading rhythms is COUNTING .

Count steady like a clock ...
ONE    TWO    ONE    TWO ...
TICK   TOCK   TICK   TOCK ...

Try counting to four and clap your hands on the count of ONE
CLAP                                       CLAP
ONE    TWO    THREE    FOUR    ONE    TWO    THREE    FOUR

You are now clapping a WHOLE NOTE rhythm.
A whole note lasts for four counts .
MORE MUSIC WRITING IDEAS
To learn more about reading rhythm check out...
NOTE DURATION
Notes are sound and RESTS are silence , to learn more...
REST DURATION