Start by learning the names of notes and their durations. The basic notes that you need to create a rhythm are the whole note, half note and quarter note. A whole note is the longest duration and holds for four beats. Think of a beat as an equally measured unit of time, similar to seconds on a clock. The half note is worth half the value of a whole note and quarter notes are worth half the value of a half note.
Create a simple rhythm once you have learned the basic note values. Create a rhythm that makes sense to you using only the basic rhythms from step one. In music there is a system of weak and strong beats. The strongest beat is the first beat of each measure followed by two or three weaker beats. A good rhythm should begin on a strong beat and end on a strong beat. Organize your rhythm to begin and end on a strong beat.
Learn about advanced rhythms including the eighth note and 16th note. The eighth note has a flag on the end of the stem and is twice as fast as the quarter note. The 16th note has two flags and is twice as fast as the eighth note. Each flag that is added to the stem will double the speed of the note. It is possible to have 32nd, 64th and 128th notes.
Download and install Musescore, a free notation program for Macintosh and Windows. Open the program and begin entering in your newly created rhythm by dragging and dropping the note values on the score. Once you are finished play the file back and listen to the rhythm created. You can even choose different instrument sounds to play your rhythm.