Word background image

Hello - I cannot for the life of me figure out how to create the background image I want for Word.  I have searched the internet all over and am frustrated.  I know there are many ways to skin a cat, but I can't seem to get any to work properly. I am working on my resumé and simply want a blue vertical bar on the left side (no white space at the side, top, or bottom.  I've inserted a shape in Word and got it to what I want. But, I want to make that a template or background image that cannot be altered or moved.  Is there a way to simply turn this into an image so I can use it as a template or background image?  If not, how can I create this image so that it is the right size? I looked up the size needed for an 8.5X11 document, but it doesn't display correctly when I copy it over (not the right size).  Maybe I'm missing the right resolution?  I feel like there has to be an easier way to do this.  Any thoughts?