Can't edit navigation bar messages buttons

Hi, I am back!
So my forum is in Latvian launguage. I decided to change navigation bar. I did change all but I can't change messages buttons. I try to change image link, but when I hit save, I get javascript message: ''You must provide menu name.''
Lol I can't change name field it's not allowed.

Can you post a print screen with the error?
Where do you upload the image?

Sorry, don't have time to take screen.

I want to upload it in navigation bar settings. By changing image link.

I'm not very sure you want , just to change the menu buttons or what ?

Yes, just change, but I cant.

Hello , check that tutorial : http://www.csshelp.net/t48-how-to-change-menu-name-in-the-navbar

No, no, no! I can't change picture.

Some images have to be changed here:
Administration Panel > Display > Colors & Pictures > Pics Management
Advanced Mode
General/Index Tab

Yes, I failed, I forgot that I can change that in pics. Thanks.