How are you running it?
I created a symlink from the installation directory into my /usr/local/bin and run it from a console.
To do this just goto your /usr/local/bin directory and type
ln -s firebird /<directory path you installed firebird to>/MozillaFirebird
This way you simply have to type firebird in the console (from any directory) to run it.
If you want to run it from a menu (like a KDE menu) then you will have to manually add a firebird entry because at this stage there is no firebird installer to do it for you.
In KDE you can do this by right clicking on the K menu and go to menu editor, add an entry Calling it Mozilla Firebird, and just put firebird as the command (if you did not do the previous symlink step, you will have to enter the full installation path).
Actually, I think I mis-understood your question, but since I've already written the previous stuff, Ill leave it just in case.
If you mean you want firebird to open if you open a html file from konqueror or something, goto the KDE control panel,
click on the components menu
click on file associations
expand the text type
click on html
Enter firebird (if you symlinked it, otherwise full path)
And move it to the top of the preference order
Hope all of this helps,
Im still reside a bit in newbie teritory myself =]