Entering the melody for the whole song is the first step.  After this step is completed you can play the song and check the melody.  In subsequent steps, the melody line will guide you as you enter chords and rhythmic values.

Suppose the complete song starts like this:

Then the first step consists in entering the melody notes ignoring chord symbols and rhythmic values.  This is done in Melody mode and in this case consists in entering this:

Recall that in Melody mode to add a melody note to the chords table you simply double click the note on the staff
with the right mouse button. This is the fastest way to enter melodies.

Although when the song is completed tie notes will not sound (see entering tie notes), you must enter them  as though there were "normal" notes.

Everywhere you encounter a rest in the written music,  enter a blank chord in the chords table.  To produce a blank chord in Melody mode, click on the button twice and then on the button.

To automatically add an altered note (such as a flat note),  first select it with the right mouse button, second click on the flat button , and third right click on the note again.