VamountainFamily - there is no such thing as a dumb question! It's all part of the learning process.
I can only help you with the adjustable strap bit though. I did my first one last week.
I got 2 D-rings and a slide adjuster piece (you can sometimes buy them as one set). Also you can use one D-ring only and sew the other end of the strap in between the lining and the body of the bag, whichever you prefer.
Thread one end of the strap through the slide adjuster centre piece, loop over the middle part of the slide adjuster and sew the end of the loop to the strap.
Then thread the other end of the strap through one d-ring then back through the slide adjuster (so it slides freely up and down the strap to adjust).
Once through the adjuster either thread the very end of the strap through the last d-ring or sew in between the 2 layers of the bag.
Make sure you're strap is long enough to slide to full length and to go shorter. I make mine quite long as I like it to sit on my hip.
I really hope this makes sense and helps you out. Its hard to describe without pics. If you're still confuzzled let me know I can put up some step-by-step pics
This drove me nuts when I first did it!