Ribbons are not menus.  They are ribbons.  In a program with ribbons, open the ribbons with alt.  Use the left and right arrow to move from ribbon to ribbon, as you would move from menu to menu.  Let's say you want to look through the view ribbon.  When you get to view, start to tab.  You will move through all the items in the view menu.  If you get to a menu, available in the ribbon in this way, press enter or space bar to open the menu.  Activate buttons in the usual way, with the space bar.  If you have problems working with structures, let us know.  There are often a lot more items in a ribbon than in one menu.  Something you intend to use regularly would be a good idea to memorize the command for.  As you move through the ribbon, such as the view ribbon, you will hear, if you let your screen-reader read to the end every time you tab, a command.  For example, this is fictitious, and if there is such a command it is coincidental, enlarge, v e.  If you press alt and then v and then e, you will activate the command or open the item, such as a menu. 

There are other commands to move faster between sections of a ribbon, but I'll let others discuss them.  I don't use ribbons enough to remember.  In other words, ribbons are generally divided into sections and you can move from section to section.  For example, an e-mail program may have a section in a ribbon named respond, where you will find commands such as reply and forward. 

Ribbon programs do have one menu you will find by left and right arrowing through the ribbons.  As you left and right arrow, you will come across something that says file, as I recall,  and it is a menu.  you may hear something else announced, I don't remember just what.  Perhaps something about a grid if you let your screen-reader read everything about the menu.  Don't worry about it.  Some common commands are in the menu such as save as.  You will see commands such as f,a, for save as in that menu.  Some of these commands will be the same as you are used to. 

Gene