What the book briefly touches on but really does not fully teach you is how to make up a bass line using a lead sheet.
OK you have a lead sheet that does not have the bass clef shown. But, it does have the chord that will harmonize a line of lyrics shown. That's all you need to compose a bass line.
Dirt simple bass lines contain notes of the active chord. How many of the notes we use is dictated by the song. And it is here that art comes into the picture, however, how to do it is quite simple; use notes of the active chord to the beat of the song - as long as the chord is active. When the chord changes then use some of those new notes in your bass line. It's really rather simple, but, you need a few things to pull it off.
This will help.
http://www.smithfowler.org/music/Chord_Formulas.htm
Roots first, fives next, the octave 8 is a safe bet and the correct 3 & 7 can fill out a bass line. Just roots work. Roots on the first beat and fives on the third beat have been in millions of bass lines.
This takes care of the root, 3, 5, 7 and 8 scale degrees. That leaves us with the 2, 4, 6. Not many chords have a 2 or 4 in their make up (sus and add) so use the 2 and 4 as passing notes, do not stop or start with them. The 6 will normally fit with major chords (R-3-5-6). So the root, 3, 5, 6, 7 & 8 are fair game and will fit nicely into a bass line - if the songs needs it. Remember the song dictates what is needed - by the space it allows for the chord's notes. Country begs for the root and five with chromatic walks to the next chord. Praise is best served with just root notes to the beat. Each style dictates what it likes.
Give it a try and see what happens. If anyone needs help with where the 3 is from the root the getting started sticky in the General Instruction section will help. From your root the 3 is always up a string and back a fret. That is where 3's live. Fives live up a string and toward the bridge two frets, or down a string same fret. Go to the sticky mentioned above and work on where each scale degree will be in relationship to your root. It's not that hard there are only 7 you have to memorize. You can get into the 9, 11 and 13 later.
Have fun.