You need to provide A LOT more information then this. What menu bar, what is the site? what do you want to do exactly? What are you using? Do you know CSS and able to change that? ETC.
I use photoshop, the menu bar at the top of the screen, especially the drop down menu to import stuff.
Many programs give you the option to make the menu items larger (ususally when you click on the upper left icon for the program). I cannot find any option to enlarge the menu items.
This is the Adobe Business Catalyst Forums section, this is about a tool that makes websites. If your after photoshop help you should look to those forums. All elements of photoshop windows are adjustable and snap to the top, side.... ETC it depends on the workspace setup you want, drag them around, configure, add, remove - It is up to you.