Watch the Vocal Exercises online guitar lesson by Karan Andrea from Guitar Player Wanted: Vocals A Plus
If these exercises all together are overwhelming or intimidating, work on the a cappella exercises only (Exercises 1-8). Those exercises work all the techniques that the rest of the exercises build on. Once you are less overwhelmed, try the consonant exercises (Exercises 9-17). Do as many as you can without feeling overloaded, and when you get comfortable with those, try the traditional exercises (Exercises 18-22).
As you improve and feel more coordinated with these exercises, I suggest that you watch sections of this course again. You will find bits of information that you either forgot about, or didn't grasp the first time through. I cover a lot of information that is difficult to comprehend all at once. This is a normal part of the learning process. Complete understanding comes with experience, of trying and failing, and then getting it right. You will get it right. Absorb as much as you can, and understand that my intent is to give you something you can grow with as you develop this new instrument you are discovering.