How to I create one menu for all pages?

Hi all,

I have a small website... I made it.
www.RonenMymon.com
It is simple and answers my needs for now...

Here is my problem...
I have the menu bar. and it is in EVERY page.
Means, when I have something to change/add, I need to change/add in EVERY page... And I have a lot of pages....

Is there a better way (I'm sure there is) and simple to create one menu bar instance for all pages? (just to update once and all pages will take from same place).
How do I do that??

And of...

How to I create one menu for all pages? WordPress ...