The easiest way to enter or change the words which match the notes of a melody, (sometimes called the "lyrics"), is to use the Staff screen, obtainable from the Edit menu, under Staff View. The words are shown under the matching notes, and you can left click on any note to permit changing the corresponding word.
However, this database screen permits minor alterations to be made directly to the database. A disadvantage is that you need to know the exact bar, beat and tick numbers for every word.
To change words on an existing tune, scroll down till you find the desired tune's FileName in the left column. Then locate the bar, beat and tick at which the word occurs. The click in the WordText field, type in the appropriate word, and hit the ENTER key.